To speak to someone with the intent of eventually engaging in sexual intercourse with them. Generally conducted in a relaxed, playful and outstandingly obvious manner.

Almost invariably carried out by men on women; to be a male recipient means you're either extremely lucky or the giver believes you, as the British say, to bat for the other side.

A common, braindead, and therefore quintessentially British phrase, which explains the strange and nonsensical definition(s) sitting next to this one. To chat up is a type of the unfortunate word of banter, which shares all three properties mentioned above.