The term 'Tool for a Guitarist' can be summarized as a CAPO, which is a four letter word. A CAPO is a device used by guitarists to raise the pitch of the strings, allowing them to play in different keys without having to change their fingering. It is typically attached to the neck of the guitar and clamped onto the strings. By using a CAPO, guitarists can easily transpose songs into different keys, making it a useful tool for any guitarist.