millionaire n 1: a person whose material wealth is valued at more than a million dollars
Millionaire \Mil`lion*aire"\ (?; 277), n. [F. millionnaire.] One whose wealth is counted by millions of francs, dollars, or pounds; a very rich person; a person worth a million or more. [Written also {millionnaire}.] [1913 Webster]
18 Moby Thesaurus words for "millionaire": Daddy Warbucks, billionaire, bloated plutocrat, capitalist, fat cat, man of means, man of substance, man of wealth, moneybags, moneyed man, multimillionaire, nabob, parvenu, plutocrat, rich man, richling, warm man, wealthy man