Answer:
The ampere has never been defined as a 'coulomb per second'. Think about it! An ampere is an SI Base Unit whereas the coulomb is a Derived Unit. So the coulomb must be defined in terms of an ampere, not the other way around!
In fact, the coulomb is defined in terms of the ampere and the second.
Until the adoption of the mksA (metre, kilogram, second, ampere) system, the ampere was defined in terms of the mass of silver deposited, by electrolysis, over a specified period. With the adoption of the mksA (and, subsequently, the SI system), the ampere has since been defined as follows:'the constant current that, if maintained in two straight parallel conductors of infinite length and negligible cross-sectional area and placed one metre apart in a vacuum, would produce between them a force equal to 2 × 10-7newtons per unit length'.
Although the ampere isn't defined in terms of a coulomb and a second, it is equivalent to a coulomb per second.