myometriumPronunciation: /ˌmʌɪə(ʊ)ˈmiːtrɪəm/Definition of myometrium noun [mass noun] Anatomy the smooth muscle tissue of the womb. Origin: early 20th century: modern Latin, from myo- 'muscle' + Greek mētra 'womb'myometrium in other Oxford dictionaries Definition of myometrium in the US English dictionary