nun tits
Breasts that are so ugly that the woman who was cursed with them should become a nun so that no man will have to look at them.
Jen's boobs look like a pair of saggy bags with stretchmarks with the ends of salamis glued to them, classic nun tits.
Nuns Tits
To describe something as completely useless. Derived from the fact that nuns do not have children, nor do they have sex, both of which are the main functions of breasts.
'Colin, you are about as much use as a pair of nuns tits.'