(literally) a black-feathered bird / (archaic) Synonym of 黒鴨 (kurogamo, “common scoter”) / (archaic) a black chicken

(Internet slang, especially anime and manga fandom) events or things from the past which one wants to whitewash/erase from history (due to it being embarrassing, poorly received, etc.); dark past

Berkshire pig

rye

a clone

rotary dial telephone / (slang) Kim Jong-un

black bamboo (Phyllostachys nigra)

(organic chemistry) cycloundecane

(organic chemistry) cyclododecane

(organic chemistry) cycloicosane