1) If one is being catty, they are being subtly or indirectly insulting. Different from bitchy in that bitchiness is just mean, while cattiness is often clever and witty, and isn't ALWAYS completely mean (for example, a catty joke). Both males and females can be and are catty.
2) Resembling a cat, feline.
Emily: Do you like this dress? I just bought it!
Bob: It's...interesting. Where did you buy it? I didn't know there were any thrift stores around here.
Emily: Wow, that was catty, Bob!