countess

from WordNet (r) 3.0 (2006)

countess
    n 1: female equivalent of a count or earl

from The Collaborative International Dictionary of English v.0.48

Countess \Count"ess\ (kount"?s), n.; pl. {Countesses} (-?s). [F.
   comtesse. See {Count} a nobleman.]
   The wife of an earl in the British peerage, or of a count in
   the Continental nobility; also, a lady possessed of the same
   dignity in her own right. See the Note under {Count}.
   [1913 Webster] Countinghouse