When you masturbate for like forever but when you finally ejaculate no semen comes out.

Like when someone lights a dynamite stick but instead of blowing up, it just fizzles out. Aka a dud!
"Maaan I wanked for hours yesterday but when I finally felt I was gonna pop, nothing came out!"

"Shit bro you totally did a rub a dud!"
by Ulgubulgu February 5, 2020
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