bum ‧ ble /ˈbʌmb ə l/ BrE AmE verb [intransitive]
[ Date: 1500-1600 ; Origin: Probably from bungle ]
1 . ( also bumble on ) to speak in a confused way, so that no one can understand you:
What was Karl bumbling on about?
2 . ( also bumble around ) to move in an unsteady way