Source : Webster's Revised Unabridged Dictionary (1913)

Bat \Bat\, n. [OE. batte, botte, AS. batt; perhaps fr. the
   Celtic; cf. Ir. bat, bata, stick, staff; but cf. also F.
   batte a beater (thing), wooden sword, battre to beat.]
   1. A large stick; a club; specifically, a piece of wood with
      one end thicker or broader than the other, used in playing
      baseball, cricket, etc.

   2. (Mining) Shale or bituminous shale. --Kirwan.

   3. A sheet of cotton used for filling quilts or comfortables;
      batting.

   4. A part of a brick with one whole end.

   {Bat bolt} (Machinery), a bolt barbed or jagged at its butt
      or tang to make it hold the more firmly. --Knight.