What does the idiom at mean?

The idiom "at" doesn't exist on its own. It's typically used in conjunction with other words to form phrases that have specific meanings.

For example:

* At all: Meaning "in any way" or "to any extent." Example: "I don't like spinach at all."

* At first: Meaning "initially" or "in the beginning." Example: "At first, I was nervous about the interview, but I calmed down."

* At least: Meaning "not less than" or "as a minimum." Example: "At least I got a good night's sleep."

* At once: Meaning "immediately" or "right away." Example: "At once, the ship started to sink."

The meaning of "at" in these phrases depends on the specific words that follow it.

Could you please give me the specific phrase you're interested in? I'd be happy to explain its meaning.