Shortened form of "Acronym Talk" referring to the abbreviated speech and terms common to im conversations and the internet in general. Words such as "lol", "rofl", "jk", "brb" all are examples of acrotalk, used either as a means of expressing emotions invisble through text or of shortening lengthy complex sentences to a few letters.
In a derogatory sense, an "acro" is an indiviual so intensly linked to the internet culture that they begin to use acrotalk in normal conversations.
Bill: Lol! That is fricking hilarious! Oh rofl!
Bobbert: Stop with that acrotalk crap you fag!
Bill: WTF!? Don't raise your voice with me! Oh, nvm. I gotta go tinkle, brb.
Bobbert: You are sooo gay...