Synonyms of the word

off-limits

• adj. Not to be entered or used; restricted.

out-of-bounds

• adj. Adjectival form of out of bounds.

restricted

• v. simple past tense and past participle of restrict.
• adj. Limited within bounds.
• adj. Available only to certain authorized groups of people.
• adj. (US, dated) Only available to customers who don't belong to racial, ethnic or religious minorities.
• adj. One of the classifications of the secrecy of an official document.
• adj. (grammar) Qualified.