<p><strong>noun</strong></p><ul><li>a shrill, whistlelike sound or loud raucous shout made to express disapproval at a theater, meeting, etc.</li><li>an instrument for producing such a sound.</li></ul><p><strong>verb</strong></p><ul><li>(used without object) to sound catcalls.</li><li>(used with object) to express disapproval of by catcalls.</li></ul><p><strong>Synonyms</strong></p><ul><li>jeer</li><li>hiss</li><li>boo</li></ul>