tabu

nouns

a prejudice (especially in Polynesia and other South Pacific islands) that prohibits the use or mention of something because of its sacred nature
taboo, tabu
an inhibition or ban resulting from social custom or emotional aversion
taboo, tabu

adjectives

forbidden to profane use especially in South Pacific islands
taboo, tabu
excluded from use or mention
"forbidden fruit"; "in our house dancing and playing cards were out"; "a taboo subject"
forbidden, out, prohibited, proscribed, taboo, tabu, verboten