all at once

adv

1. Unexpectedly; without warning; all of a sudden.

   “When all at once I saw a crowd, / A host, of golden daffodils”

   “I was on my way to the door, but all at once, through the fog in my head, I began to sight one reef that I hadn't paid any attention to afore.”

2. Used other than figuratively or idiomatically: All at the same time; all together.

   “There are too many to get in the lift all at once, so some must wait.”