o·ver·night / ˈōvərˈnīt/ • adv. for the duration of a night: they refused to stay overnight. ∎ during the course of a night: you can recharge the battery overnight. ∎ very quickly; suddenly: attitudes will not change overnight.• adj. / ˈōvərˌnīt/ for use overnight: an overnight bag. ∎ done or happening overnight: an overnight stay. ∎ sudden, rapid, or instant: Tom became an overnight celebrity.• v. / ˌōvərˈnīt/ [intr.] stay for the night in a particular place: I overnighted at the Beverly Wilshire. ∎ [tr.] ship for delivery the next day: Forster overnighted the sample to headquarters by courier.• n. / ˈōvərˌnīt/ a stop or stay lasting one night: overnights can be arranged in Kathmandu.