MSF is the term used in the context of banking in India. Full form of MSF is Marginal Standing Facility, under this scheme commercial banks can borrow funds from reserve bank of India for very short period of time.
MSF is different from repo rate in the sense that repo rate is for medium term, but banks often face liquidity crunch for short period of time ranging from 7 days to few weeks and to help them tide over this liquidity crunch this facility was introduced by the central bank, rate of interest for marginal standing facility is higher than repo rate.