Transpilers can be considered »source to source« compilers. The ouput is generally understandable by a human, different from typical compilers. Thus, the resulting output of transpilers usually still has to go through an other compiler or an interpreter to be able to be executed on a machine.
Babel or TypeScript are examples for transpilers as they transpile modern ES2015+ code to generally accepted ES5 (ES2015+ and ES5 are different versions or generations of the JavaScript language).