Dictionary.com
Thesaurus.com

marchioness

American  
[mahr-shuh-nis, mahr-shuh-nes] / ˈmɑr ʃə nɪs, ˌmɑr ʃəˈnɛs /

noun

British.
  1. marquise.


marchioness British  
/ ˈmɑːʃənɪs, ˌmɑːʃəˈnɛs /

noun

  1. the wife or widow of a marquis

  2. a woman who holds the rank of marquis

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Gender

See -ess.

Etymology

Origin of marchioness

1770–80; < Medieval Latin marchiōnissa, equivalent to marchiōn- (stem of marchiō ) marquis + -issa -ess