Call Option
Definition: An option contract that gives its holder the right (but not the obligation) to purchase a specified number of shares of the underlying stock at the given strike price, on or before the expiration date of the contract.

Call Option
Definition:

A contract between a buyer and seller whereby the buyer acquires the right, but not the obligation, to buy a specified stock, commodity or index at a predetermined price on or before a predetermined date. The seller of the option assumes the obligation of delivering the underlying, should the buyer exercise the option.

Opposite of a put option.