'Lock washer' definitions:

Definition of 'lock washer'

From: WordNet
noun
Washer that prevents a nut from loosening [syn: lockring, lock ring, lock washer]

Definition of 'Lock washer'

From: GCIDE
  • Lock washer \Lock" wash`er\, n. A washer that is not completely smooth or flat, designed to prevent a nut from loosening, placed under the nut on a screw or bolt. [1913 Webster]