SAT GRE lunacy Definition Lunacy refers to insanity or extremely foolish behavior. Example "Driving at that speed in the city is pure lunacy." Sign in to save SAT PDF — $25 GRE PDF — $25 ← lump lunar → Study tips featuring "lunacy" How Context Clues Save You on the SAT Related words SAT antonym SAT abase SAT abdicate SAT abdomen SAT abduction SAT abet SAT abeyance SAT abject SAT abjure SAT ablution SAT abnegate SAT abnormal