ballister

noun2

1. •
   A brace on a brass instrument that helps hold the valves in place.

   • Solid nickel silver ballisters and mouthpipe for longer wear, better tone, ease of blowing. — 1940
2. •
   (no longer used) A crossbow or ballista.

   • Their ramparts were armed with 3,000 ballisters to shoot javelins with and 500 catapults. — 1872