An MPI (Maximum Premium Indexing) account combines life insurance and a retirement plan. It's pitched as having the ability to compound your wealth at a higher-than-average rate while protecting your principal, eventually providing long-term tax-free retirement income, and then passing on the wealth tax-free to your heirs.
MPI stands for Maximum Premium Indexing, or, in layman's terms, a financial strategy that “could generate lots of money for you.” More specifically, though, it's a combination approach that provides life insurance and acts as a retirement planning vehicle simultaneously.
MPI takes the features of an indexed universal life insurance contract and attempts to bolster them and create new benefits. Curtis sometimes calls it IUL 2.0. See him explain it here.