1. The act or process of initiating biological reproduction by insemination or pollination.
2. The union of male and female gametes to form a zygote.
3. The act or process of applying a fertilizer.

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.