noun Biology.
existence of an organism in two or more distinct forms during the life cycle; polymorphism.
Also, pleomorphy.

1860–65; pleo- + -morph + -ism Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
pleomorphism or pleomorphy (ˌpliːəˈmɔːˌfɪzəm, ˈpliːəˌmɔːfɪ)
1.  the occurrence of more than one different form in the life cycle of a plant or animal
2.  the occurrence of more than one different form of crystal of one chemical compound; polymorphism
pleomorphy or pleomorphy
pleo'morphic or pleomorphy

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

pleomorphism ple·o·mor·phism (plē'ə-môr'fĭz'əm)

  1. See polymorphism.

  2. The occurrence of two or more structural forms during a life cycle, especially of certain plants.

ple'o·mor'phic (-fĭk) or ple'o·mor'phous (-fəs) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia Britannica


the existence of irregular and variant forms in the same species or strain of microorganisms, a condition analogous to polymorphism in higher organisms. Pleomorphism is particularly prevalent in certain groups of bacteria and in yeasts, rickettsias, and mycoplasmas and greatly complicates the task of identifying and studying them.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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