Basel Committee on Banking Supervision (BCBS)

http://www.bis.org/bcbs/index.htm

Systemically important financial institutions (SIFI) are financial institutions that are deemed systemically important to the economy in the sense that the failure of one of them could trigger a global financial crisis. Also known as "Too Big To Fail" TBTF.

As of November 2011, there is no consensual definition of what a global systemically important bank is. The Basel Committee on Banking Supervision has adopted a series of indicators that reflect the size, interconnectedness, the lack of readily available substitutes of financial institution infrastructure, their global (cross-jurisdictional) activity and their complexity.

As of July 2013, The Basel Committee of Banking Supervision have released methodology for identifying and managing global systemically important banks (G-SIBSs). Loss absorbency requirements were increased, and are scheduled for mandatory implementation by January 1st, 2019, alongside the Basel III changes. Currently, there are 30 GSIB’s according to the 2015 official list released by the FSB and BCBS.

2015 GSIB List Update: Released by BCBS and FSB Key Attributes Guidance to Assess the Systemic Importance of Financial Institutions (SB pdf)

Banks or other financial institutions whose failure would threaten the economic stability of a nation or the world financial system.

http://en.wikipedia.org/wiki/Systemically_important_financial_institution