Belt OUT is a phrase that means to SING loudly and with great enthusiasm. It is often used to describe a powerful performance of a song, where the singer is putting their all into it. The term BELT OUT can be broken down into two words, 'BELT' and 'OUT'. The crossword solution for the term BELT OUT is SING, which is a four letter word. Singing is the act of producing musical sounds with the voice, and is often done in a group or solo.