people who roam the hallways and stop in the middle to talk to their dumbass friends then when you pass nearby they say "ooooooooohhhhhhh dat nigga touch my bonkis"
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!