Any of various cosmopolitan aquatic herbs of the genus Myriophyllum, having feathery, finely dissected submersed leaves and entire or toothed emersed leaves.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.