When two people leave a large group and make strange noises that lead their friends to believe that they are having shananagins. (a.k.a. sex). Generally used when describing what two people were doing to make fun of them.
Paul: hey sara, want to go get some soda?
Sara: sure
Jim: oooh I see! you guys are gonna go have some shananagins! I see how it is!
Brad: Don't into too many shananagins!
Paul: ugh er erm NO!
Taking home a hot girl, undressing her, and realizing the vagina you've been chasing is actually a penis.
Guy friend of to another guy friend: "Man, that chickover there is so hot"
Friend: "Careful dude, it may just be a farce. Last time I took a girl that hot home is was just a shenanagina"
When you feel a situation is too wild or unbeleivabe and can not be true, you have the rights to "call shenanagins"
guy1:guess wat dude
guy2:wat
guy1:i just won the jackpot, helped cure cancer, and made out with your sister all in one night
guy2: uh-un i call shenanagins on that shit