Refering to the size of an article of clothing (usually a man's shirt) where the article is clearly bought one size too small as to display one's musclularity. Usually worn but not limited to bars, clubs, or social gathering where high numbers of attractive females tend to congregate. Commonly mistakn for a shirt you stole from your 12 yr.old brother.
–noun
1. any size Medium shirt (especially a T Shirt) worn by a man whose body-size would usually require a size Large shirt for comfort, worn for the accentuating affect it gives to musculature of the torso and arms; The resulting effect is similar to that of a medium-sized person wearing a size Small shirt.
Jeremy - "Rob, come on up here!"
Rob - "What size shirt you got on?"
Jeremy - "Fuck you."
Rob - "The price you pay when you rock a shmedium in this place."
-Season 3 Episode 8 of 'Rob Dyrdek's Fantasy Factory'