All things facing the scrotum. Point of origin. A direction that contains the polar perspective of the scrotum or "sack". The act of facing toward one's balls.
Tina has her face near Trey's crotch. She must be facing sackwards. When we drive towards that set of balls we are going sackwards.
A japanese monster (yōkai) that consists of a shadow with several eyes (sometimes a main and larger one) The shadow expands itself with tentacle-like shapes, that also end in eyes.
If you seeeyes in the middle of a very dark place, it could be backbeard.
Somebody who is deceptive, ignorant or otherwise unpleasantly cunning. Not a friendly, jovial term, a Sackhead is very much similar to a dickhead, in which said person is claimed to have a penis, or in this case a (Nut)'Sack' upon their head.