To have sex in an extremly fast, violent, but pleasurable (for both parties) event. The idea of "Fucking like a Ninja" is to get in, out, and off, before you can get caught, be it by parents, angry spouses, or even the police, in some rare occasions.

She got ninja fucked, dude. Right after they both got off, he was gone like a goddamn shadow.
by Andrew Flanagan February 26, 2006
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1.To have sex without a sound
2. To have sex without the other person knowing
You had sex last night! I didn't even hear it!
Yep, I ninja fucked her hard.
by Frickin' Genius January 14, 2016
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To have sex in a quick and intense manner.
"I could tell by the look on her face that she got ninja-fucked last night."
by Jordy-Time February 17, 2006
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To penetrate another person without that person having knowledge or noticing.
Person 1: Whoa what was that?
Person 2: You just got ninja fucked!
by mario420 September 6, 2006
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To fornicate a person, or being, without them knowing or noticing; Also slang for succesfully using the "date rape drug"
Example 1
Ninja Fucker: "That blind girl had a nice rack last night huh"

Random guy: "Word."

Ninja Fucker: "I ninja fucked the shit out of here"

Example 2

Girl 1: "Don't go to any parties at Will's house'

Girl 2: "Why not?"

Girl 1: "I heard Amanda got straight ninja fucked over there"

Example 3

Smoov-e: "I'm a Ninja Fucking master"
by DroBot January 13, 2011
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When you ( a male) is having sex with two other people ( male or female) and you fuck them in the butts back to back. Hence, you see an ASS, you see an ASS, and you went IN, or assassin ( which is a word used to describe a ninja).
Joe Schmoe: Hey bro, I just had a consecutive buttsex with these two smoking hot chicks last night
Douchebag Dan: Duuuuuude! You just had a Ninja Fuck!!!
Joe: Totally gnarly dude!!
by Jdawg96 December 18, 2013
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boy who has a large pimple on his ear that is like the rainbow, and has 2 small polka dots on the inside on them. this pimple dangles down to his balls. they make his balls smell like dirty spider webs. that are like the rainbow :) and when you run into a wall you turn into a ninja but can change to the colors of its soroundings and when you hit some one they turn pink and puff away into a booby. and if some one happens to take you to the hospital just say, a panda bit my nose off. and then give them the evil hamster in your pocket and say its a gift from budah, and then on your way home be sure to ride your elephant to Target for a box of tampons so you can give his boyfriend a dirty qujuan and then run off to your mexican lover in save him frooooooom godzilla!!!!!!!!!!
boy: man my pimple just grows by the minute!

girl: omg! was that a panda that just bit your nose!?

boy: ahhh take me to the hospital!

girl: did you give the nice man your evil hamster you got from budha?

boy: ya but i cant find my elephant......

girl: well you bes get yer lazy ass up an find it cuz i got a suprise for you.


boy: okay i found it.


boy: eww what the fuck wass that?!

girl: thatd be a dirty qujuan well i gotta go and save my mexican lover in japan from godzilla now


boys lover: godzilla no!!!!!


girl and mexican lover: nooo dont eat us!!!!!

boy: hahaha damn that sucks.

BAM a ninja fucking unicorn was born
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