The word "cockn't" means "you have no dick".Or,it can be used when chopping off somebody's dick.
Situation 1
Person 1: Wow, I'm the best
Person 2: Cockn't
Person 1: Thanks for reminding me I don't have testicles >:(
Situation 2
Person 3: Wow,I'm so cool,everyone else sucks!
Person 4: COCKN'T *chops off Person 3's dick*
Person 3: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
basically its a planned cockblock and requires the utmost creativity and epicness to pull one off. but instead of ruining the mood you just completely make it impossible.
ok ok so jimmy finally got that chick down to the apartment. so right b4 they start makin out, lets axe bomb and shaving cream bomb the room theyre in.