Verb. to stab someone with a shiv.
shank is also what retards call improvised stabbing or cutting weapons. these are not called shanks they are called shivs.
Dumbass: Dude... i just made a totally awesome shank made out of a piece of glass and tightly rolled paper.
Badass: you are dumb. you made a shiv, there is no solid thing called a shank. for being a fool, i will shank you with my shiv.