What is a binary noun?

The term "binary noun" is not a standard grammatical term. It's possible that you're thinking of a different term, or the term might be specific to a certain field or context.

Here are some possibilities:

* Binary opposition: In literary analysis, this refers to a pair of contrasting concepts or ideas that are often used to structure a story, poem, or other work of art. For example, good vs. evil, light vs. dark, or male vs. female.

* Binary code: This is a system of representing data using only two digits, 0 and 1. This is the language computers use to communicate.

* Binary data: Any data that is stored or transmitted using binary code.

* Binary star: A system of two stars orbiting around a common center of gravity.

If you could provide more context or an example of how you encountered the term "binary noun," I may be able to give you a more specific answer.