tabu

(noun) a prejudice (especially in Polynesia and other South Pacific islands) that prohibits the use or mention of something because of its sacred nature. Synonyms: taboo.

(noun) an inhibition or ban resulting from social custom or emotional aversion. Synonyms: taboo.

(adj) forbidden to profane use especially in South Pacific islands. Synonyms: taboo.

(adj) excluded from use or mention. Synonyms: forbidden, out(predicate), prohibited, proscribed, taboo, verboten. Examples: "Forbidden fruit." "In our house dancing and playing cards were out." "A taboo subject."