nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An annual European herb (Berteroa incana) of the mustard family, having silvery foliage, oblong fruits, and deeply notched white flowers. It is naturalized in eastern North America. Also called alyssum.