acorn squash

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A type of winter squash (Cucurbita pepo) shaped somewhat like an acorn and having longitudinal ridges, a variously colored rind, and yellow to orange flesh.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of several varieties of a plant, Cucurbita pepo, being a dark green winter squash having yellow to orange flesh.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun small dark green or yellow ribbed squash with yellow to orange flesh
• noun squash plant bearing small acorn-shaped fruits having yellow flesh and dark green or yellow rind with longitudinal ridges