py·ro·gal·lol 
(pī′rō-gălôl′, -ōl′, -ŏl′, -gôlôl′, -lōl′, -lŏl′)
(pī′rō-gălôl′, -ōl′, -ŏl′, -gôlôl′, -lōl′, -lŏl′)n.
A white, toxic crystalline phenol, C6H3(OH)3, used as a photographic developer and to treat certain skin diseases. Also called pyrogallic acid.
[PYRO- + GALL(IC ACID) + -OL1.]
py′ro·gallic (-gălĭk, -gôlĭk) adj.