- One time only: once a day.
- At one time in the past; formerly.
- At any time; ever: Once known, his face is never forgotten.
- By one degree of relationship: my first cousin once removed.
- A single occurrence; one time: Once will have to do. You can go just this once.
- As soon as; if ever; when: Once he goes, we can clean up.
- Having been formerly; former: the once capital of the nation.
- at once All at one time; simultaneously: Everything happened at once. The view of the skyline is at once awesome, grand, and disappointing.
- at once Immediately; instantly: Leave the room at once.