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A phenomena occurring during gay sex where the giving man's scrotum slaps the receiving man's scrotum, sending them forward to the grundle then back to hitting the giver's scrotum, which then swing backwards, and repeats.

This is derived from the desktop toy known as Newton's balls
Hannable was riding Adam so hard that the Newton's Grundle could be heard from outside the bathroom.
by horribleperson24601 April 15, 2014
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Jul 25 Word of the Day
A jack off buddy (from 'cum' /'come', meaning 'semen', and 'companion'); a friend that you get together with for sessions of solo or mutual masturbation
Variant of: cumpanion (from 'companion' & 'cum'); jack off buddy & wank bud & JO buddy
Similar to: fuck buddy
My bf and I used to really get it on together, but now it's just the occasional cumpadre wank
by Gladys Pipps-Knightley May 14, 2007
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