The term "cosmonant" is not a recognized word in standard English or any other widely accepted language. It doesn't have a conventional definition in linguistics, astronomy, or any other field.

It's possible that:

* You might have misheard or misspelled a word. Perhaps you meant "cosmonaut," which refers to a person trained to travel and work in outer space, especially in the context of the Soviet Union and Russia.

* It's a neologism or a term specific to a particular field or community. If you encountered this term somewhere specific, providing more context would help determine its meaning.

If you can provide more information about where you came across this word, I may be able to help you understand its meaning.