The thing is, if you make the definition too generic, everything turns out to be a compiler. For instance, Photoshop is a compiler that turns commands in the UI (the input language) into PSD files (the output language). It's a lot harder to define terms like "compiler" than it actually seems.
And you have to differentiate your definition for 'compiler' from 'interpreter'. And point out, that those two sit on opposite ends of the same spectrum.
Even that is a fuzzy barrier. You have lots of languages that have the compiler built-in to the runtime environment (Smalltalk, and I guess most lisps?). Anything with JIT blurrs the line, too.
A compiler is something that takes code in one language and converts it to another. It can be a Python to Javascript compiler, or a C to x86 Assembly Compiler (which can then be assembled using an appropriate assembler).
I'm reading both Louden's "Compiler Construction: Principles and Practice" and the Dragon Book. They are both good so far.