thiefthiefthievesnoun (pluralthieves)a person who steals something: A thief stole my car.word buildingA thief is a general word for a person who steals things, usually secretly and without violence. The name of the crime is theft. A robber steals from a bank, shop, etc. and often uses violence or threats. A burglar takes things from your house when you are out or asleep: • We had burglars while we were on holiday and all my jewellery was stolen.