Definition of "interchangeable"

Sometimes the same words mean opposite things. Sometimes the opposite is true. Shock absorbers are called shocks. Slow down and slow up are interchangeable.

1997, George Carlin, Brain Droppings‎, New York: Hyperion Books, page 104

The English, until relatively recently, seem to have imagined “English” and “British” to be interchangeable, as if Britain was just a bigger England.

2014 September 16, Ian Jack, “Is this the end of Britishness”, in The Guardian