Definition of what 1 a (1) — used as an interrogative expressing inquiry about the identity, nature, or value of an object or matter what is this what is wealth without friends what does he earn what hath God wrought ( 2 ) — often used to ask for repetition of an utterance or part of an utterance not properly heard or understood you said what b ( 1 ) archaic : who 1 — used as an interrogative expressing inquiry about the identity of a person ( 2 ) — used as an interrogative expressing inquiry about the character, nature, occupation, position, or role of a person what do you think I am, a fool what is she, that all our swains commend her —William Shakespeare c — used as an exclamation expressing surprise or excitement and frequently introducing a question what , no breakfast d ...