(ˌ)mərˈkapˌtal noun
( -s )
Etymology: International Scientific Vocabulary mercapt- + -al
: any of a class of compounds that are sulfur analogues of the acetals characterized by the group >C(SR) 2 , that are formed by the reaction of mercaptans with aldehydes or ketones, and that in the case of the members of low molecular weight are oily liquids of unpleasant odor