biacetyl
[ bahy-uh-seet-l, -set-l, bahy-as-i-tl ]
/ ˌbaɪ əˈsit l, -ˈsɛt l, baɪˈæs ɪ tl /
noun Chemistry.
a yellow, water-soluble liquid, C4H6O2, occurring in butter and in certain essential oils, as bay, and also synthesized: used chiefly to augment the flavor and odor of vinegar, coffee, and other foods.
Also
diacetyl.