taboo vs forbidden

taboo is a noun but forbidden is not a noun.

Word	Noun	Adjective	Verb	Adverb
taboo	Yes	Yes	Yes	No
forbidden	No	Yes	No	No

As adjectives, taboo and forbidden are synonyms defined as:

Other synonyms of taboo include out, prohibited, proscribed, tabu, verboten.

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

taboo (adjective)	forbidden (adjective)
excluded from use or mention	excluded from use or mention
forbidden to profane use especially in South Pacific islands

taboo (verb)	forbidden (verb)
declare as sacred and forbidden