A lock nut washer is...

A lock nut washer is designed with a split that allows it to grip the nut more effectively and prevent it from loosening due to vibration or other forces. This split creates tension that helps maintain a tight connection between the nut and the bolt or screw it's securing. The unique design of the split washer makes it especially suitable for applications where high levels of vibration are present, as it provides additional resistance against loosening.

The other options describe different types of washers that serve various purposes, but they do not provide the same locking feature that the split design offers. Solid washers, flat washers, and curved washers have their own specific uses, but they do not effectively prevent movement in the same way a split lock washer does.