MONDAY Meaning of MONDAY in English n. & adv. --n. the second day of the week, following Sunday. --adv. colloq. 1. on Monday. 2 (Mondays) on Monday; each Monday. Etymology: OE monand{aelig}g day of the moon, transl. LL lunae dies Oxford English vocab. Оксфордский английский словарь. 2012