"Mob: No need to ask the Godfather for forgiveness - a mob is a word for monster. Also known as creep."
"Healer: Who's keeping the tank from floor-hugging? Your powerful, puissant, never-to-be-offended healer. Seriously. Several classes can play this role and they all find it pretty much a thankless task, as people are very quick to blame healers when people die [but you won't, because you know better!]."
"Pat: Don't look around for someone androgynous - someone is warning you that a patrolling mob is coming closer and will probably [if it hasn't already] attack you. "
"Buff: Keep your clothes on. Really. "
"Inc: If there's no time to type "pat" or "adds", sometimes you'll see "inc", for "incoming". [Why is inc faster than pat? No idea.]"
Go take a look, it's not just written with its tongue in its cheek, it's actually pretty informative for new players to the game. Save time the next newbie run and just send them the URL.