for once Definition

once
adverb

1a. A single time;

Example: I'll say this only once
Thesaurus: one time, this time, never again, a single time; Antonym: repeatedly, frequently.
1b. On one occasion.

Example: They came once
2. Multiplied by one.
3. At some time in the past; formerly.

Example: lived in London once
Thesaurus: formerly, previously, earlier, in the old days, in the past, heretofore, long ago, already, before.
4. Ever; at any time.

Example: if once you are late
5. By one degree of relationship.

Example: hasn't once visited
Example: a cousin once removed

conj

1. As soon as; when once or if once.

Example: Once you have finished you can go out

noun

1. One time or occasion.

Example: just this once

Idiom: all at once

Suddenly.

All at the same time; simultaneously.

Idiom: at once

Immediately; without any delay.
Thesaurus: directly, now, right away, straightaway, this minute, without delay, instantly, unhesitatingly.

All at the same time; simultaneously.

Idiom: for once

On this one occasion if on no other; as an exception.

Idiom: once again (once more)

One more time, as before.

Idiom: once and for all (once for all)

For the last time; now and never again.

Idiom: once in a way (once in a while)

Occasionally; rarely.
Thesaurus: sometimes, occasionally, from time to time.

Idiom: once or twice

A few times.

Idiom: once upon a time

The usual way to begin fairy tales: at a certain time in the past.

Etymology: Anglo-Saxon anes, originally meaning ‘of one', from an one.