The Collaborative International Dictionary of English v.0.48:

Mugwort \Mug"wort`\, n. [AS. mucgwyrt. Cf. Midge.] (Bot.)
   A somewhat aromatic composite weed (Artemisia vulgaris), at
   one time used medicinally; -- called also motherwort.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Artemisia vulgaris
    n 1: European tufted aromatic perennial herb having hairy red or
         purple stems and dark green leaves downy white below and
         red-brown florets [syn: common mugwort, Artemisia
         vulgaris]