off-limits

US /ˌɔːfˈlɪmɪts/
UK /ˌɔːfˈlɪmɪts/
"off-limits" picture
1.

interdit, prohibé

not allowed or permitted; forbidden

:
The restricted area is strictly off-limits to unauthorized personnel.
La zone réglementée est strictement interdite au personnel non autorisé.
Talking about his past relationships is completely off-limits.
Parler de ses relations passées est complètement interdit.