From Vectorworks Developer
.VectorScript|VectorScript ..VS:Function Reference|Function Reference ..VS:Function_Reference_Appendix|Appendix
DescriptionProcedure DeleteSymbolDefinition deletes the referenced symbol definition from the document. If bCompletely is TRUE, all corresponding symbol instances will be deleted completely; otherwise, the symbol instances will be replaced with loci.
def vs.DeleteSymbolDefinition(hSymDef, bCompletely): return None
hSymDef HANDLE Handle to the symbol definition. bCompletely BOOLEAN Determines whether to replace the corresponding symbol instances with loci or delete the instances completely.