The Collaborative International Dictionary of English v.0.48:

Eggar \Eg"gar\, n. [Etymol. uncertain.] (Zo["o]l.)
   Any bombycid moth of the genera Eriogaster and
   Lasiocampa; as, the oak eggar (L. roboris) of Europe.
   [1913 Webster] egg beater

WordNet (r) 3.0 (2006):

eggar
    n 1: moth having nonfunctional mouthparts as adults; larvae feed
         on tree foliage and spin egg-shaped cocoons [syn: eggar,
         egger]