without missing a beat

Reader's Digest 9月号の記事 "Life in these United States" からの引用です。

Back to School
In high school, a classmate responded to a teacher's question with a "yo mama" joke. Without missing a beat, the teacher said, "Leave my mother out of this. I don't make the fun of your parent and look what they produced."

慣用句の様な "Without missing a beat" を調べます。

・Farlex Dictionary of Idioms: Without slowing down, pausing, or being distracted, especially in spite of a potential disruption.: Even when the hecklers started singing obnoxiously, the speaker continued without missing a beat.
・Collins COBUILD Idioms Dictionary: If someone says or does something without missing a beat, they continue to speak or do something without pausing.: `Are you jealous?' — `Only when I'm not in control,' he says, without missing a beat.