The word "yack" is a slang term used to describe someone who talks too much. Some synonyms for "yack" include blabbermouth, chatterbox, gabber, motor-mouth, and talkative. Other synonyms for this word can include "jabber", "prattle", "chit-chat", "ramble", and "gabble". Additional synonyms for "yack" may also include "gossip" and "babble". These different synonyms allow individuals to use more descriptive language when describing someone who talks excessively. It is important to understand and use different synonyms in order to communicate effectively and accurately without offending others.