the standard or lowest level on a scale of money payable, esp in taxation
base rate
noun
1.
(Brit) the rate of interest used by individual commercial banks as a basis for their lending rates
2.
(Brit, informal) the rate at which the Bank of England lends to the discount houses, which effectively controls the interest rates charged throughout the banking system
3.
(statistics) the average number of times an event occurs divided by the average number of times on which it might occur