The term CLOSEMOUTHED ONE can be described by four crossword solutions: CLAM (4 letters), CLAMS (5 letters), MUM (3 letters), and RETICENTLY (10 letters). A CLAM is a type of bivalve mollusk, which is known for its ability to close its shell tightly. Clams are often used as a metaphor for someone who is closemouthed or secretive. The word 'MUM' is an informal British term meaning 'SILENT' or 'UNCOMMUNICATIVE'. Reticently is an adverb meaning 'in a reserved or UNCOMMUNICATIVE manner'. All of these words describe someone who is not very talkative or open about their thoughts and feelings.