Adverb: at once
- Without delay or hesitation; with no time intervening
"he answered at once";
- immediately, instantly, straightaway, straight off, directly, now, right away, forthwith, like a shot [informal], right now, right off the bat [N. Amer, informal], instantaneously, outright, in a flash, tout de suite
- Simultaneously
"he took three cookies at once";
- at a time, at one time
See also: then and there