A person whose wealth is approximately half a million currency units; someone who is less than a full millionaire but significantly wealthy.
From demi- (half) and millionaire, a 19th-20th century term for the newly wealthy class that didn't quite reach millionaire status.
When millionaires became common enough to be boring, people invented 'demimillionaire' to describe people with half a million—now we just call them 'comfortable' and have billionaires to envy instead!
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