A scabby or calloused set of male / female genitalia or pubic area. The hardened and crustaceous state of the genitalia causes it to grind on their partner's reciprocal pubic area thus causing a grinding sensation.
"Jenny, why are you walking funny?"
"I'm chaffed from Reginald's girth grinder..."
OR
"Reginald, why do you scream when you pee lately?"
"Jenny's girth grinder ripped my tip off..."
"I'm chaffed from Reginald's girth grinder..."
OR
"Reginald, why do you scream when you pee lately?"
"Jenny's girth grinder ripped my tip off..."
by Ham Pony February 24, 2018
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