- The definition of a thief is a person who takes something without permission or without the owner knowing.
An example of a thief is someone who steals wallets out of back pockets.
A thief steals a woman's wallet.
thief definition by Webster's New World
Origin: Middle English ; from Old English theof, thiof, akin to German dieb ; from Indo-European base an unverified form teup-, to cower, lurk
thief definition by American Heritage Dictionary
noun pl. thieves thieves
Origin: Middle English, from Old English thēof.