option deedoption deed: a legal instrument in writing by which party A ...: a legal instrument in writing by which party A (usually called the ‘grantor’) confers on party B (usually called the ‘grantee’) a legal right to do something, for example acquire property or sharesshares: a unit in a company that quantifies what portion of ... at a predetermined price (or price formula); the instrument will usually set a limited window of time within which the option can be exercised and also the mechanics (where the option is to purchase an asset) of completing the sale and purchase following the exercise of the option.