What is Best Current Practice?

Legal Definition
A Best Current Practice (BCP) is a de facto level of performance in engineering and information technology. It is more flexible than a standard, since techniques and tools are continually evolving.

The Internet Engineering Task Force publishes Best Current Practice documents in a numbered document series. Each document in this series is paired with the currently valid Request for Comments (RFC) document. BCP was introduced in RFC-1818.

BCPs are document guidelines, processes, methods, and other matters not suitable for standardization. The Internet standards process itself is defined in a series of BCPs, as is the formal organizational structure of the IETF, Internet Engineering Steering Group, Internet Architecture Board, and other groups involved in that process.

IETF's separate Standard Track (STD) document series defines the fully standardized network protocols of the Internet, such as the Internet Protocol, the Transmission Control Protocol, and the Domain Name System.

Each RFC number refers to a specific version of a document Standard Track, but the BCP number refers to the most recent revision of the document. Thus, citations often reference both the BCP number and the RFC number.

Example citations for BCPs are: BCP 38, RFC 2827.
-- Wikipedia
Legal Definition
The current best way to do a job to reach a certain goal.