A bon mot is a witty statement, or a very well-chosen word. The most popular guest at a cocktail party is probably the one who keeps everyone chuckling with his bons mots.
In real life, we often come up with a bon mot long after a conversation is over — it's the perfect response, or the most charming way to express something. A politician who stays cool under pressure can respond to awkward questions or accusations with bons mots, and a teacher's bons mots can keep a classroom of students interested and entertained. In French, bon mot literally means "good word."