Initialism of all-trans retinoic acid.

black ink / blacking

(medicine, obsolete) The state or quality of having an excess of black bile. / Grumpiness, irritability, melancholy, moroseness.

(medicine, obsolete) Having an excess of black bile. / Characterized by melancholy. / Ill-natured; malevolent; cantankerous.

atramental

Of or relating to ink; inky; black.

(medicine, historical) Having black bile as the prevalent humor. / Characterized by melancholy or gloom.

Characterized by melancholy or glum; atrabilarious; atrabilious.

The state or quality of being atrabilarious.

(organic chemistry) A triazine herbicide that inhibits photosynthesis