mil·lion·aire (m?l?y?-nâr?)n. A person whose wealth amounts to at least a million dollars, pounds, or the equivalent in other currency.[French millionnaire, from million, million, from Old French milion; see million.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.millionaire (?m?lj??n??) or millionnairena person whose assets are worth at least a million of the standard monetary units of his or her country ?million?airess, ?million?nairess fem nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014mil?lion?aire or mil?lion?naire (?m?l y??n??r, ?m?l y??n??r) n. a person whose wealth amounts to a million or more in some unit of currency. [1820?30;