Merriam-Webster Collegiate Dictionary - initiate

 I. transitive verb  (-ated; -ating)  Etymology: Late Latin initiatus, past participle of initiare, from Latin, to induct, from initium  Date: 1533  1. to cause or facilitate the beginning of ; set going ~ a program of reform enzymes that ~ fermentation  2. to induct into membership by or as if by special rites  3. to instruct in the rudiments or principles of something ; introduce  Synonyms: see begin  • initiator noun  II. adjective  Date: 1537  1.  a. ~d or properly admitted (as to membership or an office)  b. instructed in some secret knowledge  2. obsolete relating to an ~  III. noun  Date: 1811  1. a person who is undergoing or has undergone an initiation  2. a person who is instructed or adept in some special field