A2
as a reply or reaction to something
Dictionary examples:
I sneezed loudly, and the whole class sneezed back! (0.0)
The baby made funny faces at me, so I made funnier faces back! (0.0)
My phone beeped at me, so I beeped back! (0.0)
I waved to her and she waved back. (40.2)
I'm busy at the moment - can I call you back? (41.0)