biacetyl

[bahy-uh-seet-l, -set-l, bahy-as-i-tl] /ˌbaɪ əˈsit l, -ˈsɛt l, baɪˈæs ɪ tl/
noun, Chemistry
1.
a yellow, water-soluble liquid, C 4 H 6 O 2 , 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.
Origin
bi-1 + acetyl