Jabber is a verb that means to talk rapidly, indistinctly, or unintelligibly. It can also refer to fast, incoherent, nonsensical talk or gibberish. When someone starts to jabber, they may talk on and on about something in an excited, sometimes incoherent way. The term is often used disapprovingly to describe someone who is talking too much or too quickly and is difficult to understand. Some synonyms for jabber include mouth off, rabbit on, rant, rave, and spout.