Buy To Open
A term used by many brokerages to represent the opening of a long position in option transactions.
Investopedia Commentary
Investor can buy to open either (or a combination of) puts or calls, and thus will be holding the option(s) long. The distinguishing factor of a buy to open is that the option position is not held short in the account during the transaction.
Related Links
Options Basics Tutorial
See also: Buy, Buy to Close, Call, Long, Open Interest, Option, Put, Sell to Close, Sell to Open, Short