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The wrinkly skin that separates the scrotum into the left and right hemispheres.
I was freeballing and my zipper caught my ballseam.
by mr.krinklebein May 13, 2010
The vertical seam between your balls that often turns purple during cold weather.
Man, it's so damn cold out here that my ball seam is bigger than my schlong!
by Samuel L. Bronkowitz September 14, 2007