Noun for the act of giving oral pleasure to a woman. Taken from the common name for a vagina pussy and the similarity to the action of a cat bathing itself.
The couple had a hot night, first she gave him a blow job, then he gave her a cat bath.
As I understand the term, a cat bath is pretty much synonymous with a whorebath. In that it basically involves a washcloth, soap, and a sink. Also, I believe it may be British slang.
"Dude! My, shower head was clogged, so I had to catbath in the sink to de-funk my willie."