What is a 304 woman?

There's no standard definition or classification for a "304 woman." This phrase doesn't appear in any widely known sociological, psychological, or demographic categories. It's possible:

• It's a slang term or inside joke: The phrase might be specific to a certain group, community, or online subculture. Without more context, its meaning is unclear.
• It's a reference to a specific code or system: It could be a code used within a particular organization, perhaps related to employee ID, classification, or even a fictional world.
• It's a typo or misremembered phrase: There might be a similar-sounding phrase with a known meaning.

To understand what "304 woman" means, you need to provide more context. Where did you encounter this term? What was the surrounding conversation or text? With additional information, it might be possible to decipher its meaning.