dorsum

noun

1. the posterior part of a human (or animal) body from the neck to the end of the spine

   noun.body

   Synonyms back

   Source: WordNet 3.0

2. the back of the body of a vertebrate or any analogous surface (as the upper or outer surface of an organ or appendage or part)

   noun.body

   Examples

   The dorsum of the foot.

   Source: WordNet 3.0

3. The ridge of a hill.

   noun

   Source: webster1913