OKB is a transliteration of the Russian initials of "опытно-конструкторское бюро" – opytno konstruktorskoye byuro, meaning 'experiment and design bureau'. During the Soviet era, OKBs were closed institutions working on design and prototyping of advanced technology, usually for military applications. The corresponding English language term for such a bureau's activity is R&D or "research and development."
For security, each bureau was only officially identified by a number, but were often semi-officially referenced by the name of its lead designer. For example, OKB-51 was led by Pavel Sukhoi, and it eventually became known as the OKB of Sukhoi. Successful and famous bureaus often retained these names after the death or replacement of their founding designers.
These relatively small state-run organisations were not intended for mass production of aircraft, rockets, or other vehicles or equipment which they designed. However, they usually had the facilities and resources to construct prototypes. Designs accepted by the state were then assigned to factories for mass production.
^"ПЯТЬ ДЕСЯТИЛЕТИЙ ПАВЛА СОЛОВЬЕВА" [Five Decades of Paul Soloviev] (in Russian). Research Institute for the Economics of Aviation Industry (NIIEAP). Archived from the original on 18 February 2007. Retrieved 10 July 2006.