Source : Webster's Revised Unabridged Dictionary (1913)

Frictional \Fric"tion*al\, a.
   Relating to friction; moved by friction; produced by
   friction; as, frictional electricity.

   {Frictional gearing}, wheels which transmit motion by surface
      friction instead of teeth. The faces are sometimes made
      more or less V-shaped to increase or decrease friction, as
      required.

Gearing \Gear"ing\, n.
   1. Harness.

   2. (Mach.) The parts by which motion imparted to one portion
      of an engine or machine is transmitted to another,
      considered collectively; as, the valve gearing of
      locomotive engine; belt gearing; esp., a train of wheels
      for transmitting and varying motion in machinery.

   {Frictional gearing}. See under {Frictional}.

   {Gearing chain}, an endless chain transmitted motion from one
      sprocket wheel to another. See Illust. of {Chain wheel}.
      

   {Spur gearing}, gearing in which the teeth or cogs are ranged
      round either the concave or the convex surface (properly
      the latter) of a cylindrical wheel; -- for transmitting
      motion between parallel shafts, etc.