1. Anatomy. Of, toward, on, in, or near the back or upper surface of an organ, part, or organism.
2. Botany. Of or on the outer surface, underside, or back of an organ.

[Middle English, from Late Latin dorsālis, from Latin dorsuālis, from dorsum, back.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.