cotter pin

noun

, Machinery.

1. a cotter having a split end that is spread after being pushed through a hole to prevent it from working loose.

cotter pin

noun

1. a split pin secured, after passing through holes in the parts to be attached, by spreading the ends
2. a tapered pin threaded at the smaller end and secured by a nut after insertion

Word History and Origins

Origin of cotter pin¹

First recorded in 1890–95

Example Sentences

The inspector general said the airline’s maintenance provider failed to insert a cotter pin on a critical flight control component that put some 30,000 passengers at risk.

From Reuters

Attorney Timothy Loranger says a missing safety cotter pin caused a malfunction in the helicopter’s tail rotor.

From Washington Times

On every bolt use a castellated nut and a cotter pin, or an ordinary nut and a lock washer, so the bolt will not work loose.

From Project Gutenberg

By lightly tapping in the taper cotter pin little by little, sufficient pressure is put on the cutter to make it an easy matter to completely re-face an old seat or form a new one.

From Project Gutenberg

Each bar is composed of three pieces, two side pieces from 15 ins. below to 6 ins. above springing lines and a connecting roof bar attached to the side bars by cotter pins.

From Project Gutenberg