Source : Webster's Revised Unabridged Dictionary (1913)

Cuirassier \Cui`ras*sier"\, n. (Mil.)
   In modern armies, a soldier of the heaviest cavalry, wearing
   a cuirass only when in full dress.

Cuirassier \Cui`ras*sier"\ (kw?`r?s-s?r"), n. [F. cuirassier.
   See {Curass}.]
   A soldier armed with a cuirass. --Milton.

Source : WordNet®

cuirassier
     n : a cavalryman equipped with a cuirass