A large patch of hair that grows along the lower back above one's buttocks region.

the thing that you don’t have when you’re phones percentage is over 20

One might encounter a sad trail when a human of Greek origin displays their lower back, revealing a jungle of despair. A sad trail is also the directional sign one must follow to the last stop of The Underground Railroad. The physical, and emotional opposite of the Happy Trail.

Hair down a womans buttcrack. The opposite of a happy trail.