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1 definition by Andrew Helms

 
1.
The single most important thing about a breast past the A cup.

BTNR stands for "Boob To Nipple Ratio."

A girl with a large rack and small nipples is said to have a good BTNR, while one with large nipples is said to have a bad BTNR.
"Hey bro, what's the BTNR on her?"
"Sub par. The nips are like pancakes."
by Andrew Helms November 20, 2011