Source : Webster's Revised Unabridged Dictionary (1913)

Cylinder \Cyl"in*der\ (s?l"?n-d?r), n. [F. cylindre, OF.
   cilindre, L. cylindrus, fr. Gr. ky`lindros, fr. kyli`ndein,
   kyli`ein, to roll. Cf. {Calender} the machine.]
   1. (Geom.)
      (a) A solid body which may be generated by the rotation of
          a parallelogram round one its sides; or a body of
          rollerlike form, of which the longitudinal section is
          oblong, and the cross section is circular.
      (b) The space inclosed by any cylindrical surface. The
          space may be limited or unlimited in length.

   2. Any hollow body of cylindrical form, as:
      (a) The chamber of a steam engine in which the piston is
          moved by the force of steam.
      (b) The barrel of an air or other pump.
      (c) (Print.) The revolving platen or bed which produces
          the impression or carries the type in a cylinder
          press.
      (d) The bore of a gun; the turning chambered breech of a
          revolver.

   3. The revolving square prism carrying the cards in a
      Jacquard loom.

   {Cylinder axis}. (Anat.) See {Axis cylinder}, under {Axis}.
      

   {Cylinder engine} (Paper Making), a machine in which a
      cylinder takes up the pulp and delivers it in a continuous
      sheet to the dryers.

   {Cylinder escapement}. See {Escapement}.

   {Cylinder glass}. See {Glass}.

   {Cylinder mill}. See {Roller mill}.

   {Cylinder press}. See {Press}.

Source : WordNet®

cylinder
     n 1: a cylindrical container for oxygen or compressed air
     2: a solid bounded by a cylindrical surface and two parallel
        planes (the bases)
     3: a surface generated by rotating a parallel line around a
        fixed line
     4: a chamber within which piston moves [syn: {piston chamber}]

Source : Free On-Line Dictionary of Computing

cylinder
     
         The set of {tracks} on a multi-headed {disk} that
        may be accessed without head movement.  That is, the
        collection of disk tracks which are the same distance from the
        spindle about which the disks rotate.  Each such group forms
        the shape of a cylinder.  Placing data that are likely to be
        accessed together in cylinders reduces the access
        significantly as head movement ({seeking}) is slow compared to
        disk rotation and switching between heads.
     
        (1997-07-15)