The Collaborative International Dictionary of English v.0.48:

Barrenwort \Bar"ren*wort`\, n. (Bot.)
   An herbaceous plant of the Barberry family (Epimedium
   alpinum), having leaves that are bitter and said to be
   sudorific.
   [1913 Webster]

WordNet (r) 3.0 (2006):

barrenwort
    n 1: slow-growing creeping plant with semi-evergreen leaves on
         erect wiry stems; used as ground cover [syn: barrenwort,
         bishop's hat, Epimedium grandiflorum]