Bon mot
Etymology
A direct borrowing from French "bon mot", literally "good word." English adopted the phrase in the 18th century to name the neat verbal turn prized in salon conversation, and kept the French spelling as a mark of that pedigree.
noun · /bawn MOH/
A clever, witty remark.
What it names
The polished one-liner — a single sharp saying — as distinct from sustained banter or wit in general.
Example
Wilde could ruin an argument and win the room with a single bon mot.
Related idea
A bon mot is one crafted witticism; repartee is the quick back-and-forth exchange of them — repartee is a rally, a bon mot a single perfect shot.