1.
Your parent's female cat.

If your parents paid for it, its your catsister.
If you paid for it, its your cat.
If your sibling paid for it, its your niece-kitten.

2.
A short, convienient way to say "The cat my parents adopted for me, but its still technically their cat because they paid for it. I call it my cat sometimes but my parents pay for all of her stuff. So shes like my sister except for the fact that she is a cat."

3.
A wonderful compound word that is easy to understand even if you didn't look it up on urbandictionary.

4.
Cat + sister = your sister thats also a cat. DUH RETARD SO OBVIOUS

A polite term for shoving a lubricated probe into the Earth's hole to release gas.