Someone who either directly or indirectly prevents people from having fun.
Roommate 1: Hey man, it's raining, can we smoke in the dorm?

Roommate 2: No, Roommate 3 is being a prune and is spending all day in the dorm, and he'll totally rat on us if we smoked while he was in the room.

Roommate 1: Fuck man, prunes ruin everything.
by ErrorFM February 5, 2010
a guy who wont do anything with a girl . thought to be gay
omg andrew is so prune
by boarderchick January 20, 2007
(v., Irish slang) To grab someone's testicles and squeeze hard. A common tactic of bullies in Irish schoolyards.
Damo and Anto held Paddy down while Tommo pruned him.
by UrbanDick75 November 1, 2009
a derogatory term for someone who is annoying, a party pooper, uptight, or just plain weird
Bob: Dude this is the best game ever!

Joe: Are you kidding me? Our team is losing!

Bob: But the game itself is so wonderful!

Joe: Dude, you are such a prune
by amdude11 July 25, 2010
used as an insult, more appropriately used on people whos faces actually resemble a prune.
"look at that prune"
by itchyscrot April 3, 2003
(Taken from gardening, the removal of unwanted foliage):

To erase information, usually personal information, that was posted on the Internet in an attempt to reclaim anonymity.
Having so much information available on Facebook is exposing yourself. You might want to prune it.
by Memphis Jay April 6, 2008
Someone that hasn't been winched yet. See winch
Girl 1: Are you still a prune then?
Girl 2: Yes. Are you?
Girl 1: No!
Girl 2: Who have you winched then?
Girl 1: Tell you later.
by Huni Buni May 31, 2005