The crossword solution for the term 'SOUND OF REGRET' is 'SIGH'. A SIGH is a sound that is often used to express feelings of sadness, disappointment, or regret. It is usually a deep, drawn-out exhale that conveys a sense of resignation or helplessness. Sighing is a common response to situations that are out of one's control, and it can be used to express a range of emotions from frustration to sorrow.