locknut
lock·nut
noun
1.
supplementary nut that is screwed down on a primary nut to prevent it from loosening
Origin
From lock + nut.
Related words
Broader terms
WordNet 2.1 (Princeton University). Wiktionary (CC BY-SA). WordNet 2.1 Copyright Princeton University. All rights reserved. Wiktionary content is available under the Creative Commons Attribution-ShareAlike Licence.