A person who has many millions of dollars or pounds. It is a step up from millionaire, and the step matters in how the word feels. 'Millionaire' once meant enormous wealth, but house prices and inflation have worn that down — in many cities an ordinary retired couple owning a flat is technically a millionaire. So writers reach for multimillionaire when they want the word to sound rich again. Above it sits billionaire, which is now the top of the ladder. It is a noun, and it is usually used as a label attached to a person in news and gossip writing: 'the multimillionaire businessman', 'a multimillionaire property developer'. It carries a mild edge. Depending on the sentence around it, it can be neutral fact or a quiet criticism — journalists often place it before someone's name precisely to remind readers of the gap between that person and everyone else. People almost never use it about themselves; the rich describe themselves as 'comfortable' or say nothing at all. Note also that it counts money the person has, not money that passed through their hands: someone whose company earns millions but who takes a small salary is not one.