When a man gets an erection for no apparent reason, usually in the wrong place at the wrong time.
Jimmy goes up the to front of the classroom to give a speech.
Teacher: Jimmy whats that in your pants?
Classmate: Haha he's got a murphy dick how embarrassing.
Jimmy: Shut up its not my fault!
by beerrunbandit92 September 08, 2010
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coming from the Boston area, murphy is a strong irish name. murphy's dick can be used to describe any of your Mc buddies dicks and used usually in a funny or angry manner.
I wouldn't fuck her with murphy's dick

this sucks murphy's dick
by bigpimpin978 April 20, 2011
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When you’re having an intense game of backgammon and the mother fuckers are taking too long to finish it, you quickly slam shut the backgammon set on dudes dick like a Murphy bed.
“You’re taking too long to finish this game, Jim” said David. “I know but we’re almost done and we can ride scooters to dollar general.” Jim quickly replied. “Good because in 5 more minutes I’m going to Murphy Bed That Dick.”

“Oh man, I better hurry!” Jim cried.
by DJ Nipslip July 16, 2021
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