LIBOR-OIS Spread
This spread measures the premium of one and three month LIBOR rates, the unsecured rate at which banks lend to each other, over comparable overnight index swap (OIS) rates, which show market expectations of future official interest rates set by central banks. It is a gauge of perceptions of risk in credit markets.
See also: http://research.stlouisfed.org/publications/es/09/ES0924.pdf, TED Spread