all at once

all at once  {adv. phr.}

1. Одновременно, вместе.

The teacher told the children to talk one at a time; if they all talked at one time, she could not understand them.

Bill can play the piano, sing, and lead his orchestra all at once.

2. Также "all of a sudden" — вдруг, внезапно, неожиданно.

All at once the fire alarm rang so we had to leave the building.

All at once we heard a shot and the soldier fell to the ground.

All of a sudden the ship struck a rock.

Ср.: AT ONCE.