The term 'long, slender sword' can be summarized by the word RAPIER, which is a 6-letter word. A RAPIER is a type of sword that was popular in the 16th and 17th centuries. It is characterized by its long and slender blade, which was designed for thrusting attacks rather than slashing. Rapiers were often used in duels and fencing matches, and were favored by the upper classes due to their elegant design.