I may have to organize these into categories, but I tried picking the terms most related to t-shirts. 1x1 Rib: Also 2x2 rib knit trim. The width of each rib is the same as the width between each rib. This helps the garment retain its elasticity.
Bleach wash: The process of washing fabric or a garment with bleach to soften and distress the look of the fabric.
Brushed Cotton: Cotton fabric that is brushed to remove all the excess lint and fibers from the fabric, leaving an ultra soft, smooth finish.
Cap Sleeves: A length of sleeve that hits the upper arm between the elbow and the shoulder. Generally used for ladies' garments.
Carding: A fiber cleaning process in yarn spinning.
Colorfastness: The ability of a fabric to withstand exposure to sunlight, dry cleaning and laundering without fading or running. The types of fiber, dye and treatment used for setting the color determine how colorfast a fabric will be.
Combed Cotton: Cotton yarn that has been combed to remove short fibers and straighten or arrange longer fibers in parallel order resulting in a smooth yarn used in finer garments.
Compaction: A shrinkage control technique used in fabric manufacturing.
Corduroy: Cut pile fabric woven with either wide or narrow wales formed by using extra filling. Back may be either plain or twill weave, the latter being better quality.
Cover stitch: Background of solid embroidery. Background behind copy.
Cover stitched armhole seam: Usually found in knit shirts, refers to the inside armhole seam being serged or finished.
Denier: The weight measurement of filament yarns and fibers. The low numbers represent the finer sizes and the higher numbers, the heavier yarns.
Direct embroidery: The process of sewing a name or design directly to a garment.
Double knit: A knit fabric of double thickness.
Double-Needle Stitched: A finish used on a sleeve and/or bottom hem that uses two needles to create parallel rows of visible stitching. It gives the garment a cleaner, more finished look and adds durability.
Drapability: A fabric's ability to hang gracefully in a finished product.
End-on-end: An arrangement of warp yarns with one end of color and one end of white alternatively.
Enzyme washed: A process of washing using organic substances that cause transformation or accelerate the aging of dyes.
Face: Traditionally, the side of a fabric that offers a finished or polished appearance. The face is normally used for outward print and decoration.
Feeder stripe: An 1/8" repeating stripe.
Filament: A fine or thinly spun thread or fiber.
Finish: General term for processes used in converting raw goods into finished cloth. Bleaching, mercerizing, steaming, singeing, and dyeing are typical finishing processes.
FLASH: Used in silk-screening-applying a layer of white ink on a dark garment and quickly drying before applying additional ink colors. Prevents dark garment fibers from degrading the imprint quality.
FOIL (HOT) STAMPING: The process of applying metallic or colored foil imprints with a heated magnesium die to the surface of vinyl or leather. Can be combined with debossing.
Full Cut: Refers to a garment's fit as being generous and roomy.
Garment dyed: Apparel dyed in garment form rather than fabric form. This is a popular fashion treatment used by designers.
Garment washed: After a garment is sewn it is washed to cut down on shrinkage and add softness to the garment.
Gusset: Added panel of fabric in a seam to provide action movement.
Hand: The tactile qualities of a fabric. The way it feels to the touch - soft, firm, elastic, etc.
Herringbone: Broken twill weave giving a zig-zag effect.
Interlock: A plain-stitched knit fabric which looks the same on both sides. Often used for T-shirts and golf shirts.
Jacquard: Woven-in pattern created by a special loom. A raised design or pattern woven into the fabric as opposed to being printed on the fabric.
Jersey knit: A single-knit, plain-stitched fabric with a face side that is markedly different from the back side.
Knits: Fabrics constructed by interlocking a series of loops by hand or machine. Knitted fabrics tend to mold and fit easily to body shape: woven fabrics, in contrast, drape.
Lycra: An elastomeric fiber that is blended with other fibers. Can stretch 500 percent without breaking. Holds dyes well and is resistant to heat. Trademark owned by Du Pont.
Mercerized: A treatment of fine cotton yarn or fabric that increases shine, luster and strength. Its ability to absorb dyes produces vibrant colors.
Nap: A downy surface given to a cloth when part of the fibers are raised from the basic structure and brushed.
Neck tape: Protective band of tape sewn over the seam between the shell and the collar for a more comfortable feel to the garment.
Non-woven fabrics: Materials that are produced by interlocking or bonding fabrics together.
Ottoman knit: A horizontal raised rib textured knit.
Oxford weave: A group of cotton or man-made fabrics made with a modified plain weave or basket weave. Mainly used as shirting material.
PANTONE MATCHING SYSTEM™ (PMS): An internationally recognized numerical standard of color matching artwork for reproduction on an item.
Peach wash finish: A "peach fuzz" like finish applied to washed poplin with a light nap for a soft, supple feel.
Pigment dye: Washed down colors that will continue to soften and age with washing. Great for outdoor and casual looks.
Pile fabric: Fabric with cut fibers or uncut loops which stand up densely on the surface. Usually has a plush feel (i.e., bath towel, velvet).
Pique: Knit fabric with raised lengthwise "cords" which are part of the weave.
Plain weave: The basic criss-cross method of weaving cloth.
Ply: The number of single yarns twisted together to form ply yarn; also the number of ply yarns twisted together to form cord. By twisting two or more yarns together, a stronger single yarn is created.
Poplin: A blend of cotton and polyester (bi-blend) in a poplin weave.
Printed fabric: A fabric with a pattern printed on it with an ink or dye.
Raglan sleeves: Sleeves are all one piece from collar to cuff, allowing for ease of movement.
Reactive printed fabric: A fabric printed with a reactive dye that promotes colorfastness.
Recovery: The capacity of a fabric to return to its original dimensions after being stretched out of shape.
REGISTRATION: The distance required between elements of artwork to produce a high-quality imprint. RESOLUTION: Term used when discussing requirements for specific imprint/art methods. Generally involves required "lines per inch" or "dots per inch" to produce the specified end result or quality of appearance. Rib Knit: A textured knit that has the appearance of vertical lines. It is highly elastic and retains "memory".
Ring Spun Yarn: Yarn made by continuously twisting and thinning a rope of cotton fibers. The twisting makes the short hairs of cotton stand out, resulting in a stronger yarn with a significantly softer hand.
Ripstop nylon: Nylon taffeta with double yarns creating the box pattern to provide extra strength and resistance to tearing.
Running stitch: Sequential stitching which runs in a single direction.
Sand wash: The process of washing fabric or a garment with sand to soften and distress the look of the fabric.
Seam sealing: A process in which the stitch line of a garment is made leak proof by the application of seam tape or seam-sealing glue.
Set-in sleeve: Sleeves constructed to run from the shoulder to the cuff.
Sheeting, cotton: Plain weave cotton.
Shrinkage: Terms refers to the amount of size reduction in a 100% cotton item. Most 100% items have been pre-shrunk and no more than a 4-5% shrinkage should be expected. Silicone washed: A process of washing using silicones that increase softness.
Space dye: A yarn dyeing process of which one strand received one color at irregular intervals. Produces an effect of unorganization.
Stitch count: Accumulated total of stitches required to complete and embroidery design.
Stone wash: The process of washing fabric or a garment with stone to soften and distress the look of the fabric.
Taffetta: Basic plain weave that is crisp and smooth on both sides, usually with a sheen. Warp and filling approximately of the same count. May be plain, printed, striped, checked, plaid, or antique with uneven threads.
Taped Seams: A strip of fabric sewn to the seam of a garment to prevent distortion. In outerwear, taped seams aid in waterproofing.
Texturing: To achieve a matte, cotton-like texture, a jet of air is blown on a fiber to give it a rough, non-reflective surface. Textured fibers offer greater bulk and airiness to a fabric without increasing its weight.
TINT: The percentage of a color used in an imprint area. I.E. a 50% halftone is produced by applying 50 dots per inch to the imprint area, leaving the remaining 50% without ink. Sometimes referred to as "ghosting" an imprint. Twill: A fabric whose weave is made up of 2 or 3 warp yarns or threads to every one weft. Weave with diagonal ribs and large number of variations. Diagonals may be set at sharp or blunt angles, may be embedded or raised. Important types are flannels, serges, gabardines, and surahs.
Warp: Lengthwise yarns found in all woven fabrics. The warp is stronger and denser than the weft (crosswise) yarns.
Weft: The horizontal (crosswise) threads that intersect the warp (lengthwise) threads in a woven fabric.
Weight: Usually measured in ounces per yard.
Welt: A welt is a pocket opening treatment. The welt is a cut and sewn piece of fabric that is used to finish the pocket opening.
Yarn dyed: A fabric such as plaid, check or strip where the color is in the dyed threads or yarns before weaving or knitting cloth, as opposed to the color being printed on the fabric after being woven.
T-shirt terms you may need to know before buying 
I am not a woman. I am a man. It's just a nickname. Honest.
