PRIME RATE: The interest rate banks charge their best, most credit-worthy customers. This is one of the key interest rates in the economy, and it is watched closely by financial types, government policy makers, and businesses. It's also an interest rate that should be watched closely by consumers who have loans with adjustable rates, like credit cards, that are "pegged" to the prime rate. Any movement in the prime rate triggers an automatic change in these adjustable rates. See also | interest rate | bank | federal funds rate | discount rate |