pattypan squash

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

• noun A variety of summer squash (Cucurbita pepo) having a flat round fruit with a scalloped edge, usually a white or yellow rind, and creamy white flesh.

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

• noun A summer squash notable for its small size, round and shallow shape, and scalloped edges, somewhat resembling a small toy top, or flying saucer.

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

• noun squash plant having flattened round fruit with a scalloped edge; usually greenish white
• noun round greenish-white squash having one face flattened with a scalloped edge