The Collaborative International Dictionary of English v.0.48:

Water agrimony \Wa"ter ag"ri*mo*ny\ (Bot.)
   A kind of bur marigold (Bidens tripartita) found in wet
   places in Europe.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Bidens tripartita
    n 1: bur marigold of temperate Eurasia [syn: European beggar-
         ticks, trifid beggar-ticks, trifid bur marigold,
         Bidens tripartita]