The Collaborative International Dictionary of English v.0.48:

Infield \In*field"\, v. t.
   To inclose, as a field. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Infield \In"field`\, n.
   1. Arable and manured land kept continually under crop; --
      distinguished from outfield. [Scotland] --Jamieson.
      [1913 Webster]

   2. (Baseball) The diamond; -- opposed to outfield. See
      Diamond, n., 5.
      [1913 Webster]

WordNet (r) 3.0 (2006):

infield
    n 1: the area of a baseball field that is enclosed by 3 bases
         and home plate [syn: baseball diamond, diamond,
         infield] [ant: outfield]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "infield":
   archery ground, athletic field, badminton court, baseball field,
   basketball court, billiard parlor, bowling alley, bowling green,
   course, court, cricket ground, croquet ground, croquet lawn,
   diamond, fairway, field, football field, glaciarium, golf course,
   golf links, gridiron, gym, gymnasium, ice rink, links, outfield,
   oval, playground, playing field, playroom, polo ground, pool hall,
   poolroom, putting green, racecourse, racket court, rink,
   skating rink, soccer field, squash court, stretch, tennis court,
   track, turf