Hit it hard is a saying used in the the motorcycling world,typically said by your friends or family as you set off for a ride.The reason it is said is because they dont want to see you in a wheelchair if you crash and would rather you be dead for yours and their sakes.
1- A way to tell someone to induce in a violent action against you in a really hard way. For example punching someone very hard.
2- a way to tell someone to fuck you hard.
When a person's eyebrow are so thin, or even not existent. It is assumed the person plucked their eyebrows so thin, a popular style in the 90s and early 00s, that they can no longer regrow them.