When you put a pair of pants on in a hurry over a shirt which is then tucked into the pants. Sometimes the bottom corner of the shirt sticks through your fly, which is called a T-shirt willy.
*in PE changing rooms after the lesson*

"tom, you have a t-shirt willy again"
"no i dont"
"yes you do look"
".......shit"
by ljw December 7, 2005
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