The Collaborative International Dictionary of English v.0.48:

Perissodactyla \Per`is*so*dac"ty*la\, n. pl. [NL., from Gr. ?
   odd (fr. ? over) + ? finger.] (Zool.)
   A division of ungulate mammals, including those that have an
   odd number of toes, as the horse, tapir, and rhinoceros; --
   opposed to Artiodactyla.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Perissodactyla
    n 1: nonruminant ungulates: horses; tapirs; rhinoceros; extinct
         forms [syn: Perissodactyla, order Perissodactyla]