lock nut

or locknut

  1. a nut specially constructed to prevent its coming loose, usually having a means of providing extra friction between itself and the screw.

  2. Also called jam nut. a thin supplementary nut screwed down upon a regular nut to prevent its loosening.

Origin of lock nut

First recorded in 1860–65

Words Nearby lock nut

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use lock nut in a sentence

  • When this adjustment is secured the lock nut is screwed in place so the needle valve will keep the adjustment.

    Aviation Engines | Victor Wilfred Pag
  • A lock nut (H), which has corresponding projections (IJ) is slipped over the post as shown at , and is given a quarter turn.

  • Then a coupling is cut while screwed on a pipe, so that a lock nut about 1⁄2 inch wide is made.

    Elements of Plumbing | Samuel Dibble
  • A lock nut, O, should be provided for this screw so that it will remain in adjustment.

  • The second nut is technically known as a “jam nut,” or “lock nut.”

    The Scientific American Boy | A. Russell (Alexander Russell) Bond

British Dictionary definitions for locknut


/ (ˈlɒkˌnʌt) /

  1. a supplementary nut screwed down upon a primary nut to prevent it from shaking loose

  2. a threaded nut having a feature, such as a nylon insert, to prevent it from shaking loose

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012