The top of most biterally symmetrical animals.
The concept of dorsal refers particularly to the side and upward of vertebrate animals, though the concept can be applied to many invertebrate animals as well.
Note that in bipedal apes, such as humans, dorsal still refers to the back of the animal but that the back in this case, at least while standing, is not oriented upward.
Contrast ventral. See also anterior as well as posterior.