A particularily noxious emission from ones rectum, possibly followed by a small bum nugget.
Bejesus, I just dropped a bum egg.
verb - he she it is an egg.
comes from the latin bumeus eggeus. is an extreme of the formal insult egg. taken that they are not only of a geeky persuasion but raises some question of their sexual preferance. may be used in many circles.
"Bill, can i have your rubber to erase this drawing of a penis?"
"No, because you will most likely lose it"
"hmmph! your such a bum egg!"