Blabbermouthed means a person who talks too much or reveals secrets. However, there are various antonyms for blabbermouthed, which means a person keeps a secret and is discreet. Some of the antonyms of blabbermouthed are reticent, secretive, discreet, taciturn, cautious, judicious, circumspect, diplomatic, guarded, and prudent. These antonyms describe people who are trustworthy and maintain confidentiality. They do not speak impulsively or without thinking, and they can be relied upon to keep secrets. The use of antonyms helps to enhance communication, understanding of context, and language use. It is vital to use antonyms to prevent misunderstandings in communication.