A term you call someone (you're talking to, dating, etc.) like a nickname, to let them know they are yours. Basically a playful word that sounds like an insult but is really a word to show love.
When you feed a cat cheese and it pukes, you are a dumhead.
If your name is Tony Balez and between a preference of black and white, you choose "black with a little bit of white" you are indeed a dumhead.