The Collaborative International Dictionary of English v.0.48:

Petunse \Pe*tunse"\, Petuntse \Pe*tuntse"\, Petuntze
\Pe*tuntze"\ (p[-e]*t[u^]ns"), n. [From Chinese.]
   Powdered fledspar, kaolin, or quartz, used in the manufacture
   of porcelain.
   [1913 Webster]