Top definition
A Psychotic person. Short for lunatic.
Damn that guy was chewing on his finger because he thought it was a peice of chicken. What a fucking LOON!
by Delta9 March 01, 2005
Get a loon mug for your mama Yasemin.
Aug 11 Word of the Day
A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.
"My boyfriend has a total case of brain worms. He told me the cat was bugged so the Feds could listen in on us having sex..."

or

"You totally stumbled over that entire sentence. Can't speak English all of a sudden? What, do you have brain worms?"
by _Jez_ October 03, 2009
Get a brain worms mug for your coworker Manafort.
2
A balloon filled with nitrous oxide (NOS) That is inhaled as a recreational drug
Im buying some loons tonight
by Massive log February 08, 2019
Get the Loons neck gaiter and mug.
3
In Aberdeen, Scotland, it's local dialect (doric) meaning a young guy. That's probably why there's another definition further up, for fans of the Scottish actor Billy Boyd. Whose not from Aberdeen I think but never mind.
"Aye, d'ye ken that loon fae two doors up?"
by loon July 02, 2004
Get a loon mug for your coworker Julia.
4
A crazy, psychotic person who doesn't care a.k.a nutter
by Loopyloulou September 11, 2006
Get a loon mug for your mate Callisto.
5
Crazy mofo's. Psychotics. Loonies.
Damn i went to a party last night and saw some guy get his throat sliced by a couple of Loons.
by Delta9 March 01, 2005
Get the loons neck gaiter and mug.