1. A compiler is a computer program (or a set of programs) that transforms source code written in a programming language (the source language) into another computer language (the target language), with the latter often having a binary form known as object code.
2. The translation of programs in programming, also called compilation of programs, is a systematic process that transforms any program in the input algorithmic language into some program in the object language
https://en.wikipedia.org/wiki/Compiler (1.); http://www.businessdictionary.com/definition/compiler.html (2.)