Why/when does a guy's penis pulsate?

Like is it only when your hard or is it after you ejaculate? When I was kissing my boyfriend and sitting on his lap I felt it pulsate about 4 or 5 times, then it just stopped.

Updates:
pulsating = spasm?

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Most Helpful Guy

  • If a guy has a boner he can pulsate as many times as he wants, and no it doesn't mean he jizzed in his pants.

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      Are you saying that you can do it on purpose?

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      With an erection yes.