Source : Webster's Revised Unabridged Dictionary (1913)

Pioneer \Pi`o*neer"\, n. [F. pionier, orig., a foot soldier, OF.
   peonier, fr. OF. peon a foot soldier, F. pion. See {Pawn} in
   chess.]
   1. (Mil.) A soldier detailed or employed to form roads, dig
      trenches, and make bridges, as an army advances.

   2. One who goes before, as into the wilderness, preparing the
      way for others to follow; as, pioneers of civilization;
      pioneers of reform.

Pioneer \Pi`o*neer"\, v. t. & i. [imp. & p. p. {Pioneered}; p.
   pr. & vb. n. {Pioneering}.]
   To go before, and prepare or open a way for; to act as
   pioneer.

Source : WordNet®

pioneer
     n 1: someone who helps to open up a new line of research or
          technology or art [syn: {innovator}, {trailblazer}, {groundbreaker}]
     2: one the first colonists or settler in a new territory; "they
        went west as pioneers with only the possessions they could
        carry with them"
     v 1: open up an area or prepare a way; "She pioneered a graduate
          program for women students" [syn: {open up}]
     2: take the lead or initiative in; participate in the
        development of; "This South African surgeon pioneered
        heart transplants" [syn: {initiate}]
     3: open up and explore a new area; "pioneer space"