Dictionary
cas'tellated nut'
a tall lock nut, having on its outer face radial slits allowing for insertion of a cotter pin or wire in both the nut and a hole in its bolt, so as to prevent the nut from coming loose. See illus. under
nut. Also called
castle nut. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.