This is someone who won't let you get away with anything. Someone who falls into this category usually offers a lot of tough love and tends to lack empathy for other people.
As long as you show a good level of respect in a hardass' presence, you should be fine. They prey on teenagers and those who are feeble-minded.
Person 2: Yeah, what did he do?
Person 1: He kicked me out of the house and enrolled me in the army just for skipping one class.
Person 2: Shiiiit! WHAT a hardass.
Person 1: Duuuude, I know.
Me: Awesome lets go.
Boss: Where the hell you think your going boy, get back to work!
Me: Hard ass....