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A sex act between two or more persons where the British confectionary Mars Bar is cut up into chunks or the ‘fun size’ version is used whole and inserted into the vagina and/or anus and consumed.

Can be used as part of foreplay, may be seen as part of fetish play.

Whilst this practice can be highly pleasurable, there are the associated risks of contamination of the food from anal/vaginal bacteria and fecal matter which can cause food poisoning. Females in particular run the risk of toxic shock syndrome if the item gets lost in their vagina, as well as increased risk of thrush from the sugar.
Jeremy:- you’ll never guess what Paula did last night? During sexy time she pulled a Mars Bar out of her bag, shoved it up her foof and asked me to eat it!!!
Percy:- Oh yeah, a Mars Bar party. Bet it was a king size as well, the filthy bitch. Would have to be not to get lost in her baggy vag.

I learnt about Mars Bar parties at year 7 in school, not that I understood what it meant. It was at the time Barbie Girl by Aqua was in the charts. I just remember us all ‘adapting’ the lyrics for the bit the weird bloke sang to, ‘Come on Barbie, Mars Bar Party!’ (Uh uh uh yeah!) and singing it on the no. 31 bus back from school..... happy days.
by Master of Definitions August 04, 2018
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Where a girl shoves a mars bar pussy and a guy eats it out
Hey guys theres suzzie lets have a mars bar party
by Jon Dohe January 30, 2004
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gay house party or similiar. basically a gay orgy. tend to find them in coastal towns of britain, such as brighton, bournemouth, hartlepool and seaburn.
corey and randy went to a mars bar party up the headland in hartlepool. they took sausge up the exit hole all night
by southerner in the north July 29, 2004
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