The Collaborative International Dictionary of English v.0.48:

Texas Leaguer \Tex"as Leagu"er\ [From the Texas (baseball)
   League.] (Baseball)
   A short fly that falls too far out to be handled by an
   infielder and too close in to be caught by an outfielder; --
   called also Texas league single. [Cant]
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Texas leaguer
    n 1: (baseball) a fly ball that falls between and infielder and
         an outfielder