second cousin

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

• noun A child of a first cousin of one's parent.
• noun A child of one's first cousin; a first cousin once removed.

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

• noun A grandchild of a grandparent's sibling. A grandnephew or grandniece of a grandparent.
• noun A child of a parent's first cousin.
• noun A person who shares common great-grandparents, but grandparents and parents are different.

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

• noun a child of a first cousin