What is a shadow vowel?

A "shadow vowel" is not a standard term in linguistics or phonetics. It's possible that it's being used in a specific context, but it's not a widely recognized or understood concept.

Could you please provide more context about where you encountered this term? This could help me understand what you're asking and provide a helpful response.

For example, are you referring to:

* A specific language or dialect?

* A particular phonetic phenomenon?

* An informal or slang term?

Please provide more information so I can give you a more accurate and relevant answer.