This is the act of having a raging wank whilst in the shower.
It is done to be able to fit more activities into the day by combining two activties into one without having to go through the hassle of cleaning up after a wank.
Joan: whats up with you today, normally you very angry and tense?
Colin: well i've adopted this new programme into my life called shanking which applies a wank in the same time as i shower killing two birds with one stone and without the effort of not having to clean up after my intense wanking.
A Homemade knife usually made in prison
guy:Yo i made this shank by myself
2nd guy:Don't get caught with it tho.
When one goes to the toilet for a shit, and also indulges in having a w@nk, it is referred to as a shank.
I'm going for a shank... Give me about 15
Like how you can shank corn, by peeling the outer layer off.
But a guy can also shank.
He can shank himself or a girl....
You name it.
Yo, did you hear about how chuck shanked Amanda so hard last night at the party.
-or-
Person1: you suck
Person2: you swallow
Person1: you choke
Person2: you shank
Everyone else: ohhhhhhhhhh