adverb , adjective
■ adverb / ˌəʊvəˈnaɪt; NAmE ˌoʊvərˈn-/
1.
during or for the night :
We stayed overnight in London after the theatre.
2.
suddenly or quickly :
Don't expect it to improve overnight.
■ adjective / ˈəʊvənaɪt; NAmE ˈoʊvərn-/ [ only before noun ]
1.
happening during the night; for a night :
an overnight flight
overnight accommodation
She took only an overnight bag (= containing the things needed for a night spent away from home) .
2.
happening suddenly or quickly :
The play was an overnight success.