Belonging or relating to the family Polygonaceae, which includes docks, sorrels, and knotweeds and of which the type genus is Polygonum.
Mid 19th century; earliest use found in Quarterly Journal of the Geological Society of London. From polygonum or its etymon post-classical Latin Polygonum + -aceous, after scientific Latin Polygonaceae, family name (J. LindleyNat. Syst. Bot (ed. 2, 1836) 211, replacing earlier †Polygoneae (A. L. de JussieuGenera plantarum 82)).