A side staller is by definition:

side·staller ( P ) Pronunciation Key (sid*stllr)
adjective / noun / verb

A side staller is a person that enters a public bathroom and enters the stall directly next to another individual. Side stallers are usually the lowest class, filthy people in a corporate environment. Habitual side stallers are frequently targets of bathroom beatings and practical jokes.

Also can be used as a verb, as in "I got sidestalled."
"No, a sidestaller?" adjective.
"I hate that side staller, I'm going to give him a beating when he is not looking."
by Jake Cassidy May 16, 2006
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