An abbreviation based on capitalizing the first letters of each word, acronym-style, in phrases commonly used in text messaging or "chat-speak." LOL, or "laughing out loud," is a chatcronym. As is WTF, "What the fuck!"
BRB ("Be right back"),FYI, THX ("Thanks"), and the inimitable and highly obnoxious ROFLMAO ("Rolling on the floor laughing my ass off")(which is, not coincidentally, onomatopoetically related to vomiting). Chatcronyms are to modern teen-tech communication what grunts are to a James Brown vocal: natural, somewhat crass, unselfconscious, and eminently practical. (He was, after all, a "sex machine").
Acronym typically used in chat rooms or instant messanger conversations to both shorten the amount to be typed and to convey emotion. Sometimes used by people in face to face conversation, resulting in them appearing to be complete idiots (ie a person saying lol instead of actually laughing)
lol: laughing out loud
omg: oh my god/gosh
stfu: shut the f*ck up