dunsel

noun2

1. •
   Something (especially part of a vessel) that is useless, or superfluous or unnecessary.

   • If I'm not part of the crew and earn my keep, then I'm a dunsel. And you'll not have a dunsel aboard long […] — 1982
2. •
   A captain of a vessel who has little or no practical use.

   • McCoy: “Who the blazes is ‘Captain Dunsel’?” / Spock: “Dunsel, Doctor, is a term used by midshipmen at Starfleet Academy. It refers to a part which serves no useful purpose.” — 1968