quadratusEnglishOxford New American Dictionaryquadratus /kwäˈdrādəs, kwɑˈdreɪdəs / ▸ noun (plural quadrati /-ˈdrātˌī/) Anatomy any of several roughly square or rectangular muscles, e.g. in the abdomen, thigh, and eye socket. – ORIGIN mid 18th century : from Latin, literally ‘made square’.