all at once

all at once 

1. Lit. all at the same time. The entire group spoke all at once.

2. Fig. suddenly. All at once the little girl fell out of her chair.

See also: once

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all at once

1. happening or done quickly and without any warning all of a sudden All at once I felt dizzy and had to lie down.

2. at the same time I've had to deal with too many problems all at once.

See also: once