1. A fold or a folding back.
2. A reply to an answer; a rejoinder.
3. Law. The plaintiff's response to the defendant's answer or plea.
4. An echo or reverberation.
5. A copy or reproduction.
6. The act or process of duplicating or reproducing something.
7. Biology. The process by which genetic material, a single-celled organism, or a virus reproduces or makes a copy of itself: replication of DNA.
8. In scientific research, the repetition of an experiment to confirm findings or to ensure accuracy.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.