Entry 1 sense Webster, 1913 Xyridaceous · Xyr·i·da·ceous · IPA 01 a. Of or pertaining to a natural order (Xyrideae) of endogenous plants, of which Xyris is the type. 1. Of or pertaining to a natural order (Xyrideae) of endogenous plants, of which Xyris is the type.(Bot.)