* Chat sauvage: This is the most literal translation, emphasizing the wild nature of the cat.
* Chat errant: This implies a cat that is wandering and doesn't have a home.
* Chat haret: This is more specific to a stray cat, especially one that lives in the streets of a city.
* Chat de gouttière: This literally means "gutter cat," and it's a very colloquial term for a stray or feral cat.
You could also use descriptive phrases like:
* Chat qui vit à l'état sauvage: This translates to "cat living in a wild state."
* Chat qui a été élevé dans la nature: This translates to "cat that was raised in nature."
The best choice depends on the specific situation and the nuance you want to convey.