Frictional

from WordNet (r) 3.0 (2006)

frictional
    adj 1: pertaining to or worked or produced by friction;
           "frictional electricity"; "frictional heat"; "frictional
           gearing"

from The Collaborative International Dictionary of English v.0.48

Frictional \Fric"tion*al\, a.
   Relating to friction; moved by friction; produced by
   friction; as, frictional electricity.
   [1913 Webster]

   {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.
      [1913 Webster]