The Collaborative International Dictionary of English v.0.48:

Cataphract \Cat"a*phract\ (k[a^]t"[.a]*fr[a^]kt), n. [L.
   cataphractes, Gr. ?, fr. ? covered, fr. ? to cover; kata`
   down, wholly + fra`ssein to inclose.]
   [1913 Webster]
   1. (Mil. Antiq.) Defensive armor used for the whole body and
      often for the horse, also, esp. the linked mail or scale
      armor of some eastern nations.
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   2. A horseman covered with a cataphract.
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            Archers and slingers, cataphracts, and spears.
                                                  --Milton.
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   3. (Zool.) The armor or plate covering some fishes.
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WordNet (r) 3.0 (2006):

cataphract
    n 1: armor that protects the wearer's whole body [syn: body
         armor, body armour, suit of armor, suit of armour,
         coat of mail, cataphract]