It just means "wobbly" which should be in a typical dictionary as something that moves unsteadily from side to side, as Lee said. earlier. It uses a pattern that is used in English and other languages where you add a word to a variation of itself. Here are some examples I've seen in use: Pitter-patter. Willy-nilly. Chit-chat. Hanky-panky. You can sometimes tell what they mean by just looking at them. In your example although I never heard of it I instantly knew what "wibbly-wobbly" meant because "wobbly," a real word, was in it. But with the other examples I gave you might need to look them up. People also invent these all the time. I used to call my daughter "baby bubba" for example, and I don't think I heard that anywhere.

It's a word that describes an object that sways back and forth (moving side-to-side); or an object that is very soft and flexible so as to allow for such movement.

Hahaha, I laughed when I saw this. I don't think that it is proper English and you probably saw it in Doctor Who. https://www.macmillandictionary.com/dictionary/british/wibbly-wobbly https://www.collinsdictionary.com/dictionary/english/wibbly-wobbly https://www.collinsdictionary.com/dictionary/english/wobbly https://www.urbandictionary.com/define.php?term=Wibbly