When a chick has a hairy muff, and it's never been shaved, waxed, or altered in any way. Generally seen in 70's porn accompanied by a matching head fro.
"Baby you need to do something about your flange"
"Hell no, it's all snatchural, baby"
The female analogue of a dickbrain. In other words, her actions aren't rational and decisions are totally driven by getting laid. This can refer either to the entire female or just her genitals.
Becky won't leave that bartender alone, her snatchbrain is looking for a good time!