What does @reply mean?

@reply meaning in Urban Dictionary

applied to Twitter whenever replying or giving someone a tweet. Stated aloud: "At Reply"

@reply meaning in Computer Science Dictionary

Alternatively known as a mention, @reply is a function used on Twitter to reply to another user(s) or send them a direct message. As an example, @computerhope would send a note to computerhope. To see messages directed for your requirements, select your replies loss on the Twitter profile.