Source : Webster's Revised Unabridged Dictionary (1913)

Taboo \Ta*boo"\, a. [Written also {tapu}.] [Polynesian tabu,
   tapu, sacred, under restriction, a prohibition.]
   Set apart or sacred by religious custom among certain races
   of Polynesia, New Zealand, etc., and forbidden to certain
   persons or uses; hence, prohibited under severe penalties;
   interdicted; as, food, places, words, customs, etc., may be
   taboo.

Taboo \Ta*boo"\, n.
   A total prohibition of intercourse with, use of, or approach
   to, a given person or thing under pain of death, -- an
   interdict of religious origin and authority, formerly common
   in the islands of Polynesia; interdiction. [Written also
   {tabu}.]

Taboo \Ta*boo"\, v. t. [imp. & p. p. {Tabooed}; p. pr. & vb. n.
   {Tabooing}.]
   To put under taboo; to forbid, or to forbid the use of; to
   interdict approach to, or use of; as, to taboo the ground set
   apart as a sanctuary for criminals. [Written also {tabu}.]

Source : WordNet®

taboo
     n 1: a prejudice (especially in Polynesia and other South Pacific
          islands) that prohibits the use or mention of something
          because of its sacred nature [syn: {tabu}]
     2: an inhibition or ban resulting from social custom or
        emotional aversion [syn: {tabu}]
     v : declare as sacred and forbidden

taboo
     adj 1: excluded from use or mention; "forbidden fruit"; "in our
            house dancing and playing cards were out"; "a taboo
            subject" [syn: {forbidden}, {out(p)}, {prohibited}, {proscribed},
             {tabu}, {verboten}]
     2: forbidden to profane use especially in South Pacific islands
        [syn: {tabu}]