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Either of two conjugating gametes that differ in structure or behavior, such as the small motile male spermatozoon and the larger nonmotile female ovum. Also called heterogamete.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.