To act in an inept, clumsy or inexpert manner; to make mistakes.

“Spiders build webs and wait for insects to bumble into them.”

To boom, as a bittern; to buzz, as a fly.

The act of one who bumbles; a mistake or error, especially through clumsiness.

Acting in a confused or ineffectual way; incompetent; showing little or no skill.

“a bumbling fool”