goose egg

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

• noun Zero, especially when written as a numeral to indicate that no points have been scored.
• noun A swelling or lump, especially one caused by being struck.

from The Century Dictionary.

• noun In athletic and other contests, a zero, indicating a miss or failure to score: from the resemblance of the zero-mark 0 to an egg: called in Great Britain a duck's-egg, and in the United States sometimes a round O.

from the GNU version of the Collaborative International Dictionary of English.

• Slang In games, a zero; a score or record of naught; -- so named in allusion to the egglike outline of the zero sign 0. Called also duck egg.
• A bump on the skin caused by a blow, especially one on the head.

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

• noun informal Zero; nothing.
• noun informal A swelling caused by a bump on the head.

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

• noun a quantity of no importance