MEL (Maya Expression Language) is a command line-esque language that AutoDesk Maya uses throughout its entire design. The Maya Ascii file format that scenes can be saved in uses MEL to compose its scenes. The user interface is largely built and controlled using MEL scripts. The expressions you can use to drive channels and attributes on objects are MEL.
I suppose it could technically be considered an embedded language in cases where you're just writing scripts for it. However, without MEL, Maya basically wouldn't exist. No ascii file format, no user interface, etc.
