When a guy is sitting in class and gets an unexpected/unreasoned boner. After class is through, they need to stick out thier ass while walking in order to hide it. The apperiance is similar to that of a prehistoric Tyrannosaurus rex.
Matt: Did you see that Zach kid T-Rexing out of class!?
Keith: Yea man it was so obvious.
by Plug1990 April 18, 2011
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1. Dinosaur who was considered to be the most ferocious and dangerous. Has huge teeth and mouth and can eat anything.

2. Nickname for Fibert Bruce, a man who has the physical appearance of a dinosaur, with huge teeth and a big mouth. Has been known to eat anything in sight.
"Damn... T-Rex ate all the pizza crust we left out last night. What a fucking scavenger!"
by kilo May 30, 2003
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To deliver a set of three mushroom tattoos, thus resembling a dinosaur footprint (like you made with your rubber boots in the snow when you were a child).
She smiled up at me and I couldn't resist... so I gave her the ole' T-rex.
by Ryan-michael Lindsay October 10, 2004
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The act of a girl taking it in the ass and while she's riding she's making obnoxious dinosaur noises while making her arms look like a trex
Jeff and Leah were trying the T-Rex one night and all I could hear was loud raptor like noises
by Darnelloo June 06, 2016
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A person who is so cheap that they appear to have tiny little arms like a t rex dinosaur. Their arms are too short to reach their pockets and wallet or purse. More often a girl is a t rex or t-rexer. She will never reach down to her purse to offer to pay for anything.
Yo dawg that chick is such a t rex. Every time we go out she never offers to pay for anything.
by t-rex hater January 25, 2013
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A person who is a cheapskate or pennypincher. Like the dinosaur, this person's "short arms" prevents him or her from reaching into pockets to obtain currency.
"I was buying rounds of beer all night and that T-Rex never once bought me a drink!"
by Jason Marshall September 30, 2003
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a condition in which a persons arms are shorter than the average reaching well above mid thigh usually seen with taller people (people over 6ft). Also a condition in which someone who is larger has arms that are smaller and not in proportion
if the tip of your middle finger reaches well above you mid thigh you may have t-rex arms
by jannona July 16, 2009
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