word meaning "talking boring
rubbish that nobody is interested in". Similar to babbling or rambling. For our US viewers (or anyone, really) it's what Abe Simpson
is doing when he starts one of his stories that don't go anywhere ("I had an onion tied to my belt - which was the style at the time...").
When Denis Norden or any "amusing" clip show host says stuff in between clips, they are wittering. An extremely elderly relative rambling on about the the war/their bad leg/Elsie from down the street and her lumbago would be wittering.
(For those who have asked, yes, this is a real word, I'm not making shit up, here. Ask a britnoder if you don't believe me. The Pocket Oxford Dictionary - www.xrefer.com/entry/336615 - says it means "to chatter annoyingly or on trivial matters". So there.)