A mild slang name for a penis, supposedly less offensive that cock, prick, or dick, it does not have the fecal connotations of dingleberry but is used to describe the penis in much the same circumstances by much the same people. In addition it can also be used as a mildly disparaging term for a person who has exasperated you by doing something atypically stupid.
"I had to rush like hell to get here on time. I was halfway here when I remembered I'd left the contract in my desk at home and had to go back for them, I felt like a right dooberry."
Person A: "My man, you got the utensils to pierce my shum liam lum doobily?"
Person B: "You sure you want to do that to yourself"
Person A: " Yeah dawg, I want a big ol' metal rod drilled right through my one eyed monster, but no homo shit when your down there homes"
Person B: "Iiiite then, 50 bucks and whip it out"
Person C, B, D, E and F collectively: "Oooooooh SHIT"