From The Collaborative International Dictionary of English v.0.48 :
Juncus \Juncus\ n.
The type genus of the Juncaceae, comprising the rushes;
they are perennial tufted glabrous marsh plants of temperate
regions.
Syn: genus Juncus.
[WordNet 1.5]
From WordNet (r) 3.0 (2006) :
Juncus
n 1: type genus of the Juncaceae; perennial tufted glabrous
marsh plants of temperate regions: rushes [syn: Juncus,
genus Juncus]