Dolt refers a person who isn't very smart. You might be called a dolt if you do something dumb, like stand outside your car complaining that you locked your keys inside — even though the window is wide open.
Let's be honest — you never want to be called a dolt. And if you're a kind person, you'll never call anyone else a dolt — unless they do something so frustratingly stupid that you can't take it anymore. Dolt probably came from the Middle English word dullen, meaning "to dull, make or become dazed or stupid." To help remember what dolt means, say it out loud, with gusto. With its guttural sound, the word itself sounds not very bright.