Ratch·et n.
 1. A pawl, click, or detent, for holding or propelling a ratchet wheel, or ratch, etc.
 2. A mechanism composed of a ratchet wheel, or ratch, and pawl.  See Ratchet wheel, below, and 2d Ratch.
 Ratchet brace Mech., a boring brace, having a ratchet wheel and pawl for rotating the tool by back and forth movements of the brace handle.
 Ratchet drill, a portable machine for working a drill by hand, consisting of a hand lever carrying at one end a drill holder which is revolved by means of a ratchet wheel and pawl, by swinging the lever back and forth.
 Ratchet wheel Mach., a circular wheel having teeth, usually angular, with which a reciprocating pawl engages to turn the wheel forward, or a stationary pawl to hold it from turning backward.
 Note: ☞ In the cut, the moving pawl c slides over the teeth in one direction, but in returning, draws the wheel with it, while the pawl d prevents it from turning in the contrary direction.
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 ratchet wheel
      n : toothed wheel held in place by a pawl or detent and turned
          by a lever