once

Universal Words adverb, conjunction adverb 1 on one occasion only; one time: I've only been there once. * He cleans his car once a week. * She only sees her parents once every six months. * (informal) He only did it the once. 2 at some time in the past: I once met your mother. * He once lived in Zambia. * This book was famous once, but nobody reads it today. 3 used in negative sentences and questions, and after if to mean 'ever' or 'at all': He never once offered to help. * If she once decides to do something, you won't change her mind. IDIOMS all at once 1 suddenly: All at once she lost her temper. 2 all together; at the same time: I can't do everything all at once-you'll have to be patient. at once 1 immediately; without delay: Come here at once! 2 at the same time: Don't all speak at once! * I can't do two things at once. (just) for once