overnight

Overnight is defined as something that extends from evening until morning, or something that happens very quickly.

(adverb)

If you completely change your personality from one day to the next, this is an example of when your personality changes overnight.
If you go on a trip that lasts from Monday evening until Tuesday morning, this is an example of when you go on a trip overnight.

Overnight means to ship something to be delivered the next day, or to stay somewhere for the evening and not leave until morning.

(verb)

If you FedEx something on Monday and it arrives on Tuesday, this is an example of a time when you overnight the package.
If you sleep at your friend's house and leave the next day, this is an example of a time when you overnight.

The definition of an overnight is a stop that lasts for one evening.

(noun)

If you spend one night in New York City, this is an example of an overnight.

See overnight in Webster's New World College Dictionary

adverb

adjective

noun

an overnight stay, usually one away from home

intransitive verb

to spend the night, usually away from home

See overnight in American Heritage Dictionary 4

adjective

Lasting for, extending over, or remaining during a night: an overnight trip; an overnight guest.
For use over a single night or for a short journey: overnight supplies.
Mailed for guaranteed delivery on the next day: an overnight package.
Happening as if in a single night; sudden: an overnight success.

adverb (ōˌvər-nītˈ)