what does the phrase "at once" mean in this sentence?

[Vaok]

what does the phrase "at once" mean in this sentence?

I wish I could be in two places at once.

[Conchita]

'At once' here has the sense of 'at the same time'.

[Vaok]

but I can't find the meaning of "at once "in any dictionary?

[Lost_Soul]

Really in ANY ?

http://www.thefreedictionary.com/at+once

[Mister Micawber]

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And here are SOME MORE.
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_________________
Native English teacher at Mister Micawber's

[Vaok]

thanks a lot!