any of a class of thiol compounds analogous to the alcohols, characterized by the substitution of sulfur for oxygen in the OH radical and by strong, unpleasant odors; hydrosulfide
See mercaptan in American Heritage Dictionary 4
(mər-kăpˈtănˌ)
noun
A sulfur-containing organic compound with the general formula RSH where R is any radical, especially ethyl mercaptan, C2H5SH. Also called thiol.