A Trish is a name you call a funloving, albeit immature person. To call someone a Trish, said person should be independent and somewhat selfish, laidback but sometimes offending. Trishes really define the whole 'foot in mouth' phrase. They mean well, but don't always give the best impression.
Friend-"Do i look fat?"
Trish-"Wellll, i wouldn't say you look very skinny."
Friend-"Gee thanks, way to pull a Trish."
Teacher-"These fierce seamen were called vikings."
Trish-"HAHAHA SEMEN. DID YOU HEAR HIM? HE SAID SEMEN!"