The value of an option at expiration date, i.e., the value which is received by a holder from exercising an option on expiration, ignoring the initial premium paid out to buy the option. If the option is in-the-money at expiration, and the payoff is positive enough to cover the initial premium, then exercising the option would be in the interest of its holder. Otherwise, the option will not be exercised, expiring worthless with no payoff.

It is also called a payout.