psyl·li·um (s?l??-?m)n.1. Any of several annual Eurasian plants of the genus Plantago, especially P. ovata or P. afra, having opposite leaves and small flowers borne in dense spikes.2. The seed husks of any of these plants, widely used as a mild bulk laxative and sometimes added to foods as a dietary source of soluble fiber.[New Latin, from Greek psullion, from Greek psulla, flea (from the flealike appearance of the seeds ).]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.psyllium (?s?l??m) n (Plants) a grain, Plantago psafra, the husks of which are used medicinally as a laxative and to reduce blood cholesterol levels[C16: Latin, from Greek psulla flea, due to the resemblance of the seeds to fleas]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014psyl?li?um (?s?l i ?m) n. 1. fleawort. 2. the seeds of the fleawort, used as a mild laxative esp. in breakfast cereals. [1595?1605;