look up any word, like ratchet:
 
1.
To hit someone or something with your penis.
"What sound does a tankslap make? DONG!"

"Man, if she does that to me one more time, I'm gonna tankslap that whore."
by Stovaa December 07, 2007
 
2.
The fine art of slapping one's "semi" off one's stomach to impress one's annoyed girlfriend. Also works with gay boys, apparently
I tankslapped and she was not impressed. Pah.
by The real Jeffers August 04, 2006