F.D.H
Someone who thinks they're the best at everything, even when they're clearly not.
My dad is an F. D. H. He says he can beat anyone in a race, even though he tripped over a cat last week.
My friend's cat is an F. D. H. It stares at the wall like it's the most important thing in the universe.
My teacher is an F. D. H. She says she's the best teacher ever, but I failed her class.