Buy To Close
A term used by many brokerages to represent the closing of a short position in option transactions.
Investopedia Commentary
Investor can buy to close either (or a combination of) puts or calls, and thus will be relinquishing obligations associated with the option(s). The distinguishing factor of a buy to close is that the option position must have been held short in the account during the transaction.
Related Links
Options Basics Tutorial
See also: Buy, Buy to Open, Call, Long, Open Interest, Option, Put, Sell to Close, Sell to Open, Short