Playing the marvellous instrument known as the penis by blowing and sucking in various different ways.
-girl: I'm an expert at playing the moth organ
-boy: wow, what's that? Can you show me?
-girl: okay then, drop your pants

-boy: ohhhhh mouth organ, sure 😜
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mouth organ another colorful euphemism for the act of fellatio.(sucking cock)

also known as a harmonica
I preformed on a juicy mouth organ
by utahbear September 3, 2006
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an exclamation of extreme displeasure when words such as shit, bollocks and cock just aren't enough.
Pete: hey andy, somebody just smashed your car up!
Andy: SECRET MOUTH ORGAN!!!!
by stealthy_ginger June 18, 2011
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