'Millionairess' definitions:

Definition of 'millionairess'

(from WordNet)
noun
A woman millionaire

Definition of 'Millionairess'

From: GCIDE
  • Millionairess \Mil`lion*air"ess\, n. A woman who is a millionaire, or the wife of a millionaire. [Humorous] --Holmes. [1913 Webster]