A put option is a financial contract between the buyer and seller of a securities option allowing the buyer to force the seller (or the writer of the option contract) to buy the security.

A security that you buy when you think the price of a stock or index is going to go down.

Formal contract between an option seller and an option buyer which gives the optionee the right to sell a specific contract, financial instrument, property, or security, at a specified price on or before the option's expiration date.