Polyglot
From Just Solve the File Format Problem
A polyglot is a source code or file which constitutes valid data in two or more distinct formats simultaneously.
An example of a polyglot file would be an image file which can be viewed normally, but also contains embedded ZIP data, which can be read by changing the file extension to .zip and opening it in a decompression program.
A polyglot program is source code which can be interpreted in two or more different programming languages.