Good friends usually banter back and forth easily, like they're trying to keep a step ahead of each other in witty responses. This type of banter is their special language of friendship.
Banter is both a noun and a verb about talking. It comes from unknown origins, but even as a word, it seems to be playful and teasing. You can engage in banter with friends, siblings, parents, and even good-natured strangers. Banter usually ends with everyone feeling better for the talk and verbal play. Joking, joshing, and teasing are all related to banter.