The Collaborative International Dictionary of English v.0.48:

Gypsywort \Gyp"sy*wort`\ (j[i^]p"s[i^]*w[^u]rt`), n. (Bot.)
   A labiate plant (the Lycopus Europ[ae]us). Gypsies are said
   to stain their skin with its juice.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gypsywort
    n 1: hairy Eurasian herb with two-lipped white flowers [syn:
         gipsywort, gypsywort, Lycopus europaeus]