A dead cock is the meaning for having a very sore penis. It can happen from the following.
1. Have sex so many times in 1 day.
2. Getting punched/kicked in the penis.
3. Masturbating a lot.
1. ''Hmmmm, oooowww. Fuck man! that bitch road me all night!''
2. ''I got the most deadest cock ever!, gorge is going around punching people in the cock, watch out dude.''
3. ''Wow, i never knew you could get a dead cock from masturbating a lot!, well fred don't try to wank(masturbate) 50 times in one day.I'll be out of juice the next month.''
fred: ''Hahaha, iv'e had that same experience before''