rockhead
1. slang A stupid, dimwitted person. I leave you alone for five minutes and you've already messed up the equipment's calibration. Can't you two rockheads do anything right? Janet, you rockhead, what on earth did you do that for?
2. slang Someone who abuses or is addicted to crack cocaine. You should keep your doors locked when you're driving through this part of town. There are a lot of rockheads roaming around. Tom turned into a bit of a rockhead when we were in college. Thankfully he stopped using that crap after we graduated.