The Collaborative International Dictionary of English v.0.48:

czarina \cza*ri"na\ (z?-r?"n?), n. [Cf. G. Zarin, Czarin, fem.,
   Russ. tsaritsa.]
   The title of the empress of Russia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

czarina
    n 1: the wife or widow of a czar [syn: czarina, tsarina,
         tzarina, czaritza, tsaritsa]