Source : Webster's Revised Unabridged Dictionary (1913)

Frau \Frau\, n.; pl. {Frauen}. [G. Cf. 1st {Frow}.]
   In Germany, a woman; a married woman; a wife; -- as a title,
   equivalent to Mrs., Madam.

Source : WordNet®

Frau
     n : a married German woman; used as a title equivalent to Mrs.
         in English