When a guy boasts a lot about the size of his penis, but is actually very boring and cannot last long in bed. He also tries to to sleep with as many women as possible to hide the fact that the quality of sex is really bad.
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!