The Collaborative International Dictionary of English v.0.48:

Thysanura \Thys`a*nu"ra\, n. pl. [NL., fr. Gr. ? fringe + ?
   tail.] (Zool.)
   An order of wingless hexapod insects which have setiform
   caudal appendages, either bent beneath the body to form a
   spring, or projecting as bristles. It comprises the Cinura,
   or bristletails, and the Collembola, or springtails. Called
   also Thysanoura. See Lepisma, and Podura.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Thysanura
    n 1: firebrats; silverfish; machilids [syn: Thysanura, order
         Thysanura]