[{"Bold_text": "noun", "List Items": ["a shrill, whistlelike sound or loud raucous shout made to express disapproval at a theater, meeting, etc.Synonyms: jeer , hiss , boo", "an instrument for producing such a sound."]}, {"Bold_text": "verb (used without object)", "List Items": ["to sound catcalls."]}, {"Bold_text": "verb (used with object)", "List Items": ["to express disapproval of by catcalls."]}]