A child, typically a fatherlessteenager who doesn't have any siblings nor someone to cope with when they are down.
"u are single-child lol" Suck it kid
"U have no grills??"
"go away you stupid twat"
"Get lost, you single child"
"Bruh really your an only child?"
"You're alone"
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!