navel orange

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

• noun A sweet orange that is usually seedless and has at its apex a navellike formation enclosing a small secondary fruit.

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

• A type of orange in which the fruit incloses a small secondary fruit, the rind showing on the exterior a navel-like pit or depression at the apex. There are several varieties; they are usually seedless, or nearly so, and are much grown in California.

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

• noun seedless orange enclosing a small secondary fruit at the apex