Truncation is the act of shortening something, as if a portion has been cut off. The verb 'to truncate' means to reduce the length of something by removing part of it. Truncated is an adjective that describes something that has been shortened, like a truncated picnic due to a sudden downpour. The verb 'to truncate' means to cut or shorten.
You can truncate a board that is too long with an electric saw, a chainsaw or even a karate kick.