An acronym for the phrase "Totally Fucking Lost", which is used to describe a person who is very out of place in a certain situation and, as a result, is behaving in a manner that is awkward and/or annoying (typically without realizing)
Origin: Washington, DC; Philadelphia, PA
"That old alumnus guy who was at the college bar by himself and never stopped shouting things at the screen during the game seemed like he was trying to impress all the students there with his fanhood and football acumen. It was really obnoxious. He was so TFL."