all at once (not comparable)
- (idiomatic) Unexpectedly; without warning; all of a sudden.
- William Wordsworth, Daffodils
- When all at once I saw a crowd, / A host, of golden daffodils
1913, Joseph C. Lincoln, chapter 4, in Mr. Pratt's Patients:
- 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.
- Used other than as an idiom: All at the same time; all together.
- There are too many to get in the lift all at once, so some must wait.