What is "ichthyol"

Ichthyol \Ich"thy*ol\, n. [Gr. 'ichqy`s, -y`os, a fish + (prob.) L. oleum oil; but cf. Ichthyolite.] (Chem.) An oily substance prepared by the dry distillation of a bituminous mineral containing fossil fishes. It is used in medicine as a remedy in some forms of skin diseases.

n. (context medicine English) The ammonium salt of bitumen sulfonate; used to treat some forms of skin diseases