pbo

from The Collaborative International Dictionary of English v.0.48

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}.
   [1913 Webster +PJC]

   Note: Massicot is sometimes used by painters, and also as a
         drier in the composition of ointments and plasters.
         [1913 Webster]