look up any word, like b4nny:
 
1.
To joke on someone, to pull a fast one; to be mischevious and devious in intent and nature; to fool someone or lead them on thinking one thing, only to have them unpleasantly surprised about the true result
Guy puts in work all night for this girl at a party. As they go upstairs and get ready to have sex, the girl passes out before anything happens. The guy's response, SHANANAGAINS.
by pbpimpn4life25 May 16, 2007
 
2.
A word used when one person claims he/she will do/say something and you think they won't.The penalty for not doing what they said they would (when a shananagains is called ) results in them being hit in the balls / boobs by the shananagee , ( person who calls shananagains ).
person 1:I swear im going to kill him someday.
person 2:shananagains!
by kyle c smith May 18, 2008