A glorious creature which to the naked eye is cute but will rip you up and make an omelet out of you. Beware for the egg dog will make you bleed with cuteness and will cause you to fill up your camera roll with photos. Then, it will crack you like an egg.
Bob - Look! It is an egg dog!!!
Jeff - Oh damm. Mate, I'm sorry.
A dog that eats eggs out of a hen house. Such a dog is considered low down and no damn good. A scoundrel or nefarious person can also be called and egg-sucking dog. Reference Johny Cash's song "Dirty Old Egg Sucking Dog".
Although this definition is based on a state supreme court case in which a dog was sentenced to death for raiding a chicken coup, the term is most commonly used as a metaphor.
This literally refers to a seriously ugly or mangy mongrel. Said to be descrbed this way because of its non-doglike penchant for eating the insides of eggs.
Metaphorically, it can be applied to a person (almost always male) who is out-and-out riff-raff: one of the inbred corps.