"dorsum" in the noun sense
1. back, dorsum
the posterior part of a human (or animal) body from the neck to the end of the spine
"his back was nicely tanned"
2. dorsum
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
"the dorsum of the foot"
Source: WordNet® (An amazing lexical database of English)
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