growth ring

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

• noun A growth layer in secondary xylem seen in a cross section of a woody stem or branch.
• noun A layer of calcareous material or other substance deposited in a single period of growth of an animal, as in an otolith or a turtle scute.

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

• noun Any of the concentric rings formed in the trunk of a tree by the annual growth of wood

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

• noun an annual formation of wood in plants as they grow