IPA: /ˈkloʊsˌmaʊθd/
KK: /ˈkloʊsˌmaʊθd/
Not willing to speak or share information; reserved or secretive in communication.
He remained closemouthed about his plans for the future.
Closemouthed → It is formed from "close" (from Old English "clōsan", meaning to shut or seal) and "mouthed" (from "mouth", which comes from Old English "muð", meaning the opening of the face). The word "closemouthed" describes someone who keeps their mouth shut or is secretive.
Think of someone who 'shuts' ('close') their 'mouth' — that's why closemouthed means being secretive or not talking.