The Collaborative International Dictionary of English v.0.48:

minors \minors\ n.
   The minor leagues, those leagues of professional sports
   teams less proficient than the majors, or major leagues.

   Syn: minor league.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

minors
    n 1: a league of teams that do not belong to a major league
         (especially baseball) [syn: minor league, minors, bush
         league]