Mot qui témoigne d’une précision lexicale dans la formulation d’une idée et qui rend mieux que tout autre mot une nuance de sens.

Antonyme : impropriété.

A word that ensures lexical precision in the formulation of an idea and that renders the nuance of the sense better than any other word.

English was apparently unable to come up with its own mot juste to refer to a word or phrase that expresses exactly what the writer or speaker is trying to say and so borrowed the French term instead. The borrowing was still very new when George Paston (pen name of Emily Morse Symonds) described a character’s wordsmithery in her 1899 novel A Writer’s Life thusly: “She could launch her sentences into the air, knowing that they would fall upon their feet like cats, her brain was almost painlessly delivered of le mot juste….” As English speakers became more familiar with the term they increasingly gave it the English article “the” instead of the French “le”.

The interpreter paused, choosing le mot juste before speaking.
— New York Times, 17 Mar. 2020

2- Antonym : inappropriate expression.