# castle nut

> English word · Noun

## Definitions
1. A nut with rounded extensions projecting past the nut's opening. A cotter pin is inserted through a hole in the bolt and bent around the castle nut's projections to lock the nut in place.

## Etymology
The projections resemble the turrets of a castle.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/castle-nut