Be a heckler is an expression that refers to someone who makes rude comments or shouts out insults during a performance. It is derived from the verb 'HECKLE, ' which means to harass or annoy with questions, challenges, or gibes. To be a heckler is to engage in this behavior, usually in a public setting such as a theater or sporting event. The crossword solution for this term is 'JEER, ' which is another word for heckling. Jeering is the act of making loud, mocking, or derisive comments.