The vicarious pleasure a man derives from seeing another man's penis being serviced sexually, usually by imagining himself in the same situation. In other words, the reason some straight men cannot enjoy lesbian porn.
For me it's either hardcore or futanari; gotta get my penis empathy.
Where a woman or other person without a penis understands the pain a man goes through when he gets hit in the junk, or has otherwise painful experiences related to his private square.
Man, I feel some real penis empathy for that guy who just got a tattoo on his dick. That's gonna hurt for months.