1. prep. In, near, or in the general vicinity of a particular place.
Caesar was at Rome; at the corner of Fourth Street and Vine; at Jim’s house
2. prep. (indicating time) (Indicating occurrence in an instant of time or a period of time relatively short in context or from the speaker's perspective.)
at six o’clock; at closing time; at night.
3. prep. In the direction of (often in an unfocused or uncaring manner).
2. adv. (temporal location) Formerly; during some period in the past.
He was once the most handsome man around. I once had a bicycle just like that one.
Wang notes that flowers have rooted and grow in the area once covered with ice.
Example Sentences
We'll all go in at once.
Because you would have to drink ten gallons of spit from someone who's infected all at once.
It's a lot of people to snuff at once.
You can't get that by downing a teaspoon all at once.
He is at once in awe of his commanding officer, but with the inbred arrogance of his aristocratic background.