well its when two people either rub their own nuts at the name time thinking of another person (so its like they are rubbing each others nuts)...OR when two people rub their nuts against each other.
Hey you wanna rubnuts?.....
-whats that?.....
-"well.. its when you rub you nuts..."
-"yea alright"
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!