Synonyms of forbidden

2 Syllables
vetoed, undue, banned, taboo, pathless, trackless, closed, no-no
3 Syllables
contraband, refused, outlawed, verboten, proscribed, illegal, closed-down, closed-up, unlawful
4 Syllables
undeserved, unlicensed, extralegal, impassable, untouchable
5 Syllables
unmentionable, under-the-counter
6 Syllables
unconstitutional