1, A phrase used in the UK to summarise someone's conversational ability. Usually used when speaking to a friend about someone you've just spoken to for the first time. This is the noun form of 'chat'.
2, When used as a verb to "chat" means to talk at ones leisure, usually to mates.
3, Chatting (same meaning as the above).
4, "Chatting up", distinctively different from the former. It means to speak flirtatiously with someone you usually intend to sleep with.
1, "Mate, that birds fit but her chat stinks!"
"I don't like your chat boy!"
2, "Just go chat to him and sort it out!"
"Alright mate, Haven't seen you in ages! Fancy going for a pint and a chat a bit later on?"
3, "What you chatting bout?"
"He was in there chatting away"
4, "Mate see that bird over there? I started chatting her up, but it turned out she has a fellah!"