Someone who has only a mustache with no other facial hair or sideburns.
His justache looks like he's sniffin a sick caterpiller
Moustache without a beard, goatee, or any other facial hair.
Alex: How many justaches do you think we'll see at the Cork tonight?
Tyson: Over/under is 3...and I'll take the over. Think I just saw Magnum P.I. walk into Jam Session.