The sack that holds your "nards"... a "scrotum" (abbr. "scrote"), or "ballbag" ("baw'bag" in scotland). Also known as the "wee guys' hammock" since it is the resting place of the little baby machine spermees.
'Watch it, or I'll boot you in the nardsack so hard it'll bust, and you're wee guys will spill freely onto the floor"
Often refers to someone in baseball with unusually large testicles making it uncomfortable to manoeuvre them self in a comfortable manner. One who is called ' Nardsack' is prone to lash out after making an error.