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A split cotter inserted through a hole or holes and bent at the ends to fasten two or more parts together.
1. (Mechanical Engineering) a split pin secured, after passing through holes in the parts to be attached, by spreading the ends
2. (Mechanical Engineering) a tapered pin threaded at the smaller end and secured by a nut after insertion
a cotter having a split end that is spread after being pushed through a hole to prevent it from working loose.