milk·weed (m?lk?w?d?)n. Any of various plants of the genus Asclepias, having milky juice, usually opposite leaves, variously colored flowers grouped in umbels, and pods that split open to release seeds with downy tufts.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.milkweed (?m?lk?wi?d) n1. (Plants) Also called: silkweed any plant of the mostly North American genus Asclepias, having milky sap and pointed pods that split open to release tufted seeds: family Asclepiadaceae. See also asclepias2. (Plants) any of various other plants having milky sap3. (Plants) orange milkweed another name for butterfly weed4. (Animals) another name for monarch3Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014milk?weed (?m?lk?wid) n. 1. any of several plants of the genus Asclepias, characterized by a milky juice, clusters of white-to-purple flowers, and pods filled with silky tufted seeds. 2. any of various other plants having a milky juice, as certain spurges. [1590?1600] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.