oversummer UK /ˌəʊ.vəˈsʌm.ə/US /ˌoʊ.vɚˈsʌm.ɚ/ verb1 •To spend the summer (in a particular place or form).The snails (Bakerilymnaea cockerelli) oversummer in the adult or near-adult morphology using a form of estivation. — 1976 formsoversummered · oversummering · oversummers