Source : Webster's Revised Unabridged Dictionary (1913)

Polygonaceous \Pol`y*go*na"ceous\, a. [See {Polygonum}.] (Bot.)
   Of or pertaining to a natural order of apetalous plants
   ({Polygonace[ae]}), of which the knotweeds (species of
   {Polygonum}) are the type, and which includes also the docks
   ({Rumex}), the buckwheat, rhubarb, sea grape ({Coccoloba}),
   and several other genera.

Polygonum \Po*lyg"o*num\, n. [NL., fr. Gr. ? a kind of plant;
   poly`s many + go`ny the knee, a joint of a plant. So called
   in allusion to the numerous joints.] (Bot.)
   A genus of plants embracing a large number of species,
   including bistort, knotweed, smartweed, etc.

Source : WordNet®

Polygonum
     n : diverse genus of herbs or woody subshrubs of north temperate
         regions [syn: {genus Polygonum}]