1Less advanced in mental, physical, or social development than is usual for one's age.
- 1.1informal Very foolish or stupid.‘in retrospect, it was a totally retarded idea’
- 1.1informal Very foolish or stupid.
In the sense less advanced in development than is usual for one's ageretarded dates from the late 19th century. It has acquired offensive connotations in recent decades, and terms such as developmentally disabled or having intellectual disabilities are now preferred in many contexts