What does “potable” mean in French?

On a tap or a sign, potable means safe to drink — eau non potable is the warning worth recognising at a French campsite or station. In casual speech the word slides sideways: c’est potable means acceptable, passable, and nothing more. A haircut, a film or an essay can all be potable. It is faint praise, the verdict on something that will do.

Dictionaries mark that second sense as familier, so keep it for conversation rather than a written report, and note the standard intensifier: tout juste potable is “only barely acceptable.” The drinking sense is the older one — potable goes back to Latin potare, “to drink,” which also gave French une potion.