1. holla back - Noun
2. holla back - Verb
(informal) A holler back; a reply.
(informal) An echo of voices, much like the response of a crowd to a cheerleader.
(informal, uncountable) Feedback.
(informal) To reply.
(slang) To make or respond to romantic or sexual overtures.
(informal) To contact again at a later time.
Source: en.wiktionary.org