A person whose wealth equals at least one billion dollars, making them extraordinarily rich.
From French 'billion' (one thousand million) + suffix '-aire' (one who has). The word entered English in the 1800s as global wealth increased. 'Million' comes from Latin 'mille' (thousand), and 'billion' adds another 'bi-' (two) for scale—literally 'two million' in some countries.
The word 'billionaire' is actually quite young—it barely existed before the 1900s because so few people had that much wealth. Now billionaires are common enough that we have sub-categories like 'multibillionaire,' showing how wealth inequality has grown exponentially.
Complete word intelligence in one call. Free tier — 50 lookups/day.