Definition of polygonaceous in US English:

polygonaceous

adjective

Botany
  • Belonging or relating to the family Polygonaceae, which includes docks, sorrels, and knotweeds and of which the type genus is Polygonum.

Origin

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. Lindley Nat. Syst. Bot (ed. 2, 1836) 211, replacing earlier † Polygoneae (A. L. de Jussieu Genera plantarum 82)).