A dog tail is when a man finishes intercourse with a woman doggy style but keeps the tip of his penis located at the lips of the woman's vagina. It is called a dog tail because from a side view the woman looks like a dog on her hands and knees with a tail.
I was watching my roommate have sex with this girl in such a position that from the side it looked like she was a dog with a dog tail.
A stubborn or rigid person, who never changes himself or his attitude even through hardships or in unfavorable circumstances
my friend was imprisoned two years back now he is released but he has not changed at all , he has not mended his ways, he still do the criminal activities , he seems to be a "Dog Tail" which can never be straighten even kept in the pipe for long.