Definition of water-hemp in US English:

water-hemp

noun

  • 1Water agrimony, especially Eupatorium cannibinum (now rare).

  • 2US any of several North American plants of the genus Amaranthus (family Amaranthaceae), especially A. cannabinus, a tall marsh plant with willow-like leaves and greenish-yellow flowers, and A. tuberculatus, a troublesome agricultural weed.

Origin

Mid 16th century; earliest use found in John Withals (d. c1555), lexicographer.