ONE TIME › one time: It's only snowed once or twice this year. I go swimming once a week (= one time every week).
NOT NOW › in the past, but not now: This house once belonged to my grandfather.
once again › again: Once again I'm left with all the washing up.
all at once › suddenly: All at once he stood up and walked out of the room.
at once › immediately: I knew at once that I would like it here. › at the same time: They all started talking at once.
once in a while › sometimes but not often: He plays tennis once in a while.
once and for all › If you do something once and for all, you do it now so that it does not have to be dealt with again: Let's get to the bottom of this matter once and for all!
once more › one more time: If you say that once more, I'm going to leave.
for once › used to mean that something is happening that does not usually happen: For once, I think I have good news for him.
once upon a time › used at the beginning of a children's story to mean that something happened a long time ago → See also once in a blue moon