The Collaborative International Dictionary of English v.0.48:

Bevel gear \Bev"el gear`\ (Mech.)
   A kind of gear in which the two wheels working together lie
   in different planes, and have their teeth cut at right angles
   to the surfaces of two cones whose apices coincide with the
   point where the axes of the wheels would meet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bevel gear
    n 1: gears that mesh at an angle [syn: bevel gear, pinion and
         crown wheel, pinion and ring gear]