The Collaborative International Dictionary of English v.0.48:

Fleabane \Flea"bane`\, n. (Bot.)
   One of various plants, supposed to have efficacy in driving
   away fleas. They belong, for the most part, to the genera
   Conyza, Erigeron, and Pulicaria.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fleabane
    n 1: hairy perennial Eurasian herb with yellow daisylike flowers
         reputed to destroy or drive away fleas [syn: fleabane,
         feabane mullet, Pulicaria dysenterica]
    2: any of several North American plants of the genus Erigeron
       having daisylike flowers; formerly believed to repel fleas
    3: common North American weed with linear leaves and small
       discoid heads of yellowish flowers; widely naturalized
       throughout temperate regions; sometimes placed in genus
       Erigeron [syn: horseweed, Canadian fleabane, fleabane,
       Conyza canadensis, Erigeron canadensis]