The Collaborative International Dictionary of English v.0.48:

Notchweed \Notch"weed`\, n. (Bot.)
   A foul-smelling weed, the stinking goosefoot (Chenopodium
   Vulvaria).
   [1913 Webster]

WordNet (r) 3.0 (2006):

Chenopodium vulvaria
    n 1: European goosefoot with strong-scented foliage; adventive
         in eastern North America [syn: stinking goosefoot,
         Chenopodium vulvaria]