shortend version of Trenchcoat, a duster like longcoat commonly worn in black or tan. black is viewed my many to be the more styleish and/or threatining.
confers cred only if you got it from a thrift store or a friend as they are damn expensive bought new.
"woah dude where did you get the trench?"
"it was like, 3 bucks at good will"
"sweet!"