adj, n, v. Usually refers to a female, sometimes a female teacher, who nobody likes. Some synonyms can include "stingy", "penguin", or "waddle waddle".
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!