1. In Investing, on the National Best Bid and Offer (NBBO) this is the point at which market orders are executed against an available eligible contraorder, once submitted through International Securities Exchange. When the midpoint price is better than the limit price, limit orders are executed at the midpoint . 2. In General, this is the failure to pay principal or interest owed by a borrower on a set date to the lender. A mortgagor failing to pay the lender on time is at monetary default.