Source : Webster's Revised Unabridged Dictionary (1913)

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

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

   2. (Baseball) The diamond; -- opposed to {outfield}. See
      {Diamond}, n., 5.

Source : WordNet®

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