Other forms: morons
When your little brother does something that is both stupid and infuriating, you'll have to bite your tongue to keep from calling him a moron. A moron is an unkind way to describe someone who is foolish and unintelligent.
The word moron was an official term in the early 1900s, used to describe a person of low intelligence — specifically, an "adult with a mental age between eight and twelve." It became a popular insult in the 1920s, and gradually stopped being used as a medical term, until moron was only an informal way to put someone down.