The act of placing one's testicles firmly between someone else's breasts, or "topping" the breasts with the "nuts".
Person 1 - "I feel like our sex life has become repetitive, and I want to try something new "
Person 2 - "I've always wanted to try 'nut topping'. It sounds like it would be fun!"
A derivative of "top left", top left nut is used in a hostile manner to tell someone to "get lost"; to fuck off.
That's cap, Katy. Top left nut.
The highest price you're willing to pay for an item.
"My top nut on that is like 30 bucks."