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 A plant of either of the genera Gnaphalium and Filago: so named from the soft white pubescence that covers it.
• 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.

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