the GNU version of the Collaborative International Dictionary of English
n. A subordinate part.
The Century Dictionary and Cyclopedia
To divide (a part) and assign subordinate portions of it.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a part lying on the lower side or underneath an animal's body
Word Usage
"And now I saw that there did seem to be a mighty long rock laid across the topmost part of the upstanding rock, and yet had a very strange and shapely appearance; and did seem upon the underpart to be as that I had lookt before upon it."