The Collaborative International Dictionary
Lead protoxide
massicot \mas"si*cot\, n. [F. massicot; E. masticot is a corruption.] (Chem.) Lead monoxide (also called Lead protoxide), PbO, obtained as a yellow amorphous powder, the fused and crystalline form of which is called litharge; lead ocher. It is used as a pigment. It is also called lead oxide yellow, as opposed to red lead, which is lead tetroxide Pb3O4.
Note: Massicot is sometimes used by painters, and also as a drier in the composition of ointments and plasters.