A fraction of an inch, because men often exaggerate the lengths of their members.
If, on average, a man with a five inch penis claims it's six inches long, then a penis inch is 5/6 of an inch.
The window is forty penis inches wide, but really it's only three feet.
How you refer to a same sex partner if you do not wish to implicitly come out to the person to whom you are speaking.
"I didn't want those guys to know I was gay, so I called Jack my spouse."