A disgusting individual who steals the property (woman) of a man through conniving acts of flirtatious conversation and/or sexual relations. All women previously dated by a man are owned by him for a period of 3 months unless given express permission by the owner.
When representing a sly dog in picture form it is best to use the poodle.
Every school on the planet should have a SDRB (sly dog review board) that reviews cases of sly doggery to decide if it is a true example of sly doggery. Punishments include forced periods of abstinence, ball destruction, and death among other things.
When bringing evidence to the SDRB remember that picture evidence is, the best evidence.
Ben: "Did you see Alex sly dogging my girl? He practically groped her!'
Jack: "No, do you have evidence?"
Ben: "Here's a picture"
George was getting along well until Ben sly dogged his girl. Now she doesn't even notice him.