Something extremely difficult/tough or physically rugged and unbreakable.
Can be used to for both physical and mental descriptions.
Dave: Damn, I think I failed that test man, it was cockhard!
Ray: No, you're just stupid.
Dave: My shoulder hurts ever since you body-slammed me on that cockhard floor!
to go in big, act wide, spend and die.
Dude, Jeff went cockhard down to Vegas. Haven't seen him for a week.