A small twitch of the penis caused by sexual thoughts or stimuli.
"Okay, sir, could you pull down your pants so I could have a look at the problem. Just relax, sir, nothing to be embarassed about."
"Certainly."
"Ah okay, it seems to be a standard skin condition on the top of the penis, nothing to worry about. My 20-year-old daughter had the same thing on her breasts. She..."
"..."
"Oh dear, I'm sorry about that twitch it just did."
"In the profession we call that a nano-boner!"
by Autonova May 06, 2010

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