Yabba Hubba (pronounced yabba hooba) is an adjective which shares the same meaning as "good", "ok", or even "fun".
(Aiden spills milk from the fizzy drink section)
Chris: That wasn't very Yabba Hubba
or
(Aiden & Chris absolutely demolish a group of vandal youths inside a museum)
Chris: Mate that was a Yabba Hubba moment.
Aiden: Aye mate aye mate aye mate it was a Yabba Hubba moment.