valerian

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

• noun Any of several plants of the family Valerianaceae, especially Valeriana officinalis, native to Eurasia and widely cultivated for its small, fragrant, white to pink or lavender flowers and for use in medicine.
• noun The dried rhizomes of Valeriana officinalis, used medicinally as a sedative.

from The Century Dictionary.

• noun A plant of the genus Valeriana.
• noun The rootstocks of the officinal valerian, or some preparation from them.
• Pertaining to any one of the name of Valerius

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

• noun (Bot.) Any plant of the genus Valeriana. The root of the officinal valerian (Valeriana officinalis) has a strong smell, and is much used in medicine as an antispasmodic.
• noun (Bot.) a plant (Polemonium cæruleum) with blue or white flowers, and leaves resembling those of the officinal valerian.

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

• noun A hardy perennial flowering plant, Valeriana officinalis, with heads of sweetly scented pink or white flowers.
• noun More generally, any plant of the genus Valeriana.
• noun uncountable The root of Valeriana officinalis, used in herbal medicine.

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

• noun a plant of the genus Valeriana having lobed or dissected leaves and cymose white or pink flowers