Definition of at once in English:

at once

1Immediately: I fell asleep at once
More example sentences
  • When using oil, the mixture should be combined as quickly as possible, then baked at once.
  • The call goes to Birkenshaw who have files on all the area and can direct a fire crew to me at once.
  • If it is broken it must be used at once, for it discolours and spoils quickly.
Synonyms
immediately, right away, right now, this moment/instant/second/minute, now, straight away, instantly, instantaneously, directly, suddenly, abruptly, summarily, forthwith, promptly, without delay/hesitation, without further ado;
quickly, as fast as possible, as soon as possible, fast, speedily, with all speed
informal like a shot, in/like a flash, before you can say Jack Robinson, in two shakes (of a lamb's tail)
2At the same time; simultaneously: computers that can do many things at once
More example sentences
  • There was a slow churning of his thought processes as two ideas came together at once.
  • In the low light of the gallery the effect is at once beautiful and rather ominous.
  • Everything is happening at once at the moment, in a manner that is proving really rather hard to deal with.
Synonyms
at the same time, at one and the same time, at the same instant/moment, (all) together, simultaneously;
as a group, in unison, in concert, in chorus
See parent entry: once

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