To reply to or talk to someone, either online or face-to-face. (from the practice of targeting a message or reply to someone online by writing @name)

“Cars 2 is the most influential film of all time. Don't @ me.”

The at sign (@).

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”

(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.”

In the direction of (often in an unfocused or uncaring manner).

“He threw the ball at me.  He shouted at her.”