For me, the "human-readable" part is key. It's not just that the output is e.g. javascript, but that it is more or less human-readable with about the same organization as the original code.
If you implement SKI combinators, or three-address instructions, as functions in javascript, and that's the output of your compiler, I would not call that a transpiler.
If you implement SKI combinators, or three-address instructions, as functions in javascript, and that's the output of your compiler, I would not call that a transpiler.