Someone who bumbles; a person who mumbles, stumbles over their words, or is hard to understand, and frequently carries themself strangely, trips, or is otherwise inelegant while walking.
One who posts non-stop on Tumblr, the blog website. Often talks about his/her latest post or 'reblog'. Similar to the twitter shitter. Can also be full of self-righteousness.
Bumbler: "Yo, Mike, did you see that post of me talking about pointless stuff on my Tumblr this morning?"
Mike: "No, bumbler, and I don't give two shits in a handbasket, you goddamn Tumblr bumbler."
A hum bumbler is the person at the party who is too drunk to sing the song, so they just hum it. Also they take it in the ass, wherein, bumbler becomes involved. SEE muff diver