(slang) Sometimes shortened to: yak. Means noisy, continuous, and trivial talk or conversation, chatter; gossip or to talk a lot, usually about nothing important: e.g. That's enough yackety-yak. Quiet! They've been yakking on the phone for over an hour. The Sergeant...only talks when he has something to say. Everybody else goes yacketty-yack all the time

"yackkety-yakking" means "continuously talking without stopping" or "talking non-stop" Here are some examples" "I don't like Clare, she is always yackkety-yakking about her troubles." "Those people in the movie theatre were so rude! They didn't stop yackkety-yakking the whole time!" This expression is a little old though. I don't hear many people use it these days. :]

It means: talking sop