A
locknut, also known as a
lock nut,
locking nut,
prevailing torque nut,
stiff nut or
elastic stop nut, is a
nut that resists loosening under vibrations and torque. Elastic stop nuts and prevailing torque nuts are of the particular type where some portion of the nut deforms
elastically to provide a locking action. The first type used fiber instead of nylon and was invented in 1931.