The process of making something optional.

(US, military, aviation) An aircraft that may be manned or unmanned, able to function in either mode without modification.

plural of optionally piloted vehicle

(naturism) Allowing and encouraging nudity but tolerating the wearing of clothes, as between nudist and clothing compulsive. Abbreviation: C.O.

(finance) An option that can be exercised only at expiry date.

(finance) An option that can be exercised at specific dates between issue date and expiry date. Sometimes known as a mid-Atlantic option.

(finance) an option that can be exercised at any date between the issue date and the expiry date.

(business, often attributive) A business practice in which a customer agrees to have goods or services provided automatically, and must either continue to pay for the service or specifically decline before being rebilled.

plural of option button

(graphical user interface) A radio button.