Systemically Important Financial Institution
From ACT Wiki
(SIFI.)
A financial firm whose disorderly failure would because of its:
(i) Size,
(ii) Complexity, and
(iii) Systemic interconnectedness
cause significant disruption to the wider financial system and to economic activity in its (main) country or region of operation.
The idea wasw developed for banks considered too big to fail. It has been exended to other types of institutions and the Financial Stability Oversight Council in the US, for example, has provisionally identified certain insurance comapnies and investors as potential US SIFIs.