cottonweed

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various plants having cottony down, as some species of the genus Froelichia.

from The Century Dictionary.

• noun Same as sea-cudweed.
• noun The common milkweed, Asclepias Syriaca: the name, like that of silkweed, refers to the copious white fiber attached to its seeds. Also called wild cotton.
• noun A plant of either of the genera Gnaphalium and Filago: so named from the soft white pubescence that covers it.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) See cudweed.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of several unrelated plants that have downy heads, but especially such plants of the genus Froelichia.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an American everlasting having foliage with soft wooly hairs and corymbose heads with pearly white bracts
• noun any of various plants of the genus Froelichia found in sandy soils and on rocky slopes in warmer regions of America; grown for their spikes of woolly white flowers