The Collaborative International Dictionary of English v.0.48:

Henbit \Hen"bit`\, n. (Bot.)
   A weed of the genus Lamium (Lamium amplexicaule) with
   deeply crenate leaves.
   [1913 Webster]

WordNet (r) 3.0 (2006):

henbit
    n 1: Eurasian plant having toothed leaves and small two-lipped
         white or purplish-red flowers [syn: henbit, Lamium
         amplexicaule]