piceous

adjective2

1. •
   Resembling pitch in colour; a very dark brown.

   • Picirostris. Oblong, black: silvery-silky: snout half way and legs piceous. — 1806
2. •
   (no longer used, rare) Of or pertaining to pitch (“a sticky, dark brown substance obtained from distilling turpentine or wood tar, or crude oil or tar”); having a quality like pitch.