unjust enrichment

noun | unjust en·rich·ment

1. : the retaining of a benefit (as money) conferred by another when principles of equity and justice call for restitution to the other party; also : the retaining of property acquired especially by fraud from another in circumstances that demand the judicial imposition of a constructive trust on behalf of those who in equity ought to receive it — see also quasi contract 1 at contract : the retaining of property acquired especially by fraud from another in circumstances that demand the judicial imposition of a constructive trust on behalf of those who in equity ought to receive it — see also quasi contract 1 at contract

2. : a doctrine that requires an equitable remedy on behalf of one who has been injured by the unjust enrichment of another