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.