backdoor surprise 

v./n. inf(!) to unexpectedly penetrate someone's anus; often, of a heterosexual couple engaged in doggy style intercourse, when the male withdraws from the vagina, and hilariously re-inserts into the anus without prior warning.

NOT to be confused with the equally amusing Cadbury Surprise.

Betty: ... but then, as I... as I was about to... come, for some reason he pulled out... and then... *breaks down sobbing* he.. he put it... oh god! *sobs uncontrolably*
Psychiatrist 1: He gave you a BACKDOOR SURPRISE!? What a guy!!!
*hi-fives Psychiatrist 2*
Psychiatrist 2: Man, that is awesome!

backdoor surprise by Terry Deary July 21, 2008

St. Louis Backdoor Surprise 

Putting Molly in someone's asshole while fucking.

Popularized in St. Louis by Cardinal fans

She gave me the St. Louis backdoor surprise after the Cardinals' game.

St. Louis Backdoor Surprise by buttchug32 October 10, 2025

backdoor surpise 

When your having sex doggiestyle, and then you pull it out and stick it in her ass.

Dude i was fuckin her doggystyle and then i gave her a backdoor surprise

backdoor surpise by JamesBong February 3, 2004

backdoor suprise 

to bang someone anally without warning

i was making dinner and jim gave me a backdoor suprise

backdoor suprise by jewmongler588 June 14, 2011

back door surprise 

the act of reaching ones hand around anothers bottom and sneaking an object in said butt hole/crack

last night i totally hit my gf with a back door surprise, she loved it

back door surprise by butt grabber11 March 16, 2009