A term used mostly by gay men to depict something unpleasant, foul, or undesirable. Often replaces words such as stupid, dumb, gay, etc. Ugh, this is so vaginal, I have to work a 9 hour shift today! Those pants are straight up vaginal.
Warning signs such as fear and/or nervousness around other dogs, displays of aggression only under certain circumstances (while on leash, in the presence of food, in the presence of the owner, etc.), or most commonly, over-the-top play behavior can be seen at any stage of the dog's development.
The tug-causing-dominance-issues thing is absolutely FALSE. Some dogs have a herding instinct, but they are fiercely protective of their human counterparts and would not hurt them. If you train your dog and treat it well, then tug is a game that just strengthens the bond between a dog and its owner.