French phrase
Je suis indisponible.
Meaning
I'm unavailable.
When to use it
A brief way to say that availability is not possible. It is common in scheduling and service contexts, with a somewhat formal tone. An alternative can make it sound more accommodating.
Example dialogue
Tu peux venir demain à dix heures ?
Can you come tomorrow at ten?
Je suis indisponible. On peut se voir vendredi ?
I'm unavailable. Can we meet on Friday?