1. Someone who probably spends way too much time "stumbling" on the website Stumble Upon.
2. Someone who gets extreme, almost narcotic pleasure from searching the web randomly via a trained/custom program like Stumble Upon
3. Yo mama.
Sam is such a Stumblebum! I wish she'd quit junking up my Facebook wall with that weird $#*!
Someone whom stumbles and fumbles around lol!
Steve from Late Night with Conan O'Brien is a stumblebum.