sunflower

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

• noun Any of several plants of the genus Helianthus of the composite family, especially H. annuus, having tall coarse stems and large, yellow-rayed flower heads that produce edible seeds rich in oil.
• noun A brilliant yellow to strong or vivid orange yellow.

from The Century Dictionary.

• noun A plant of the genus Helianthus, so named from its showy golden radiate heads.
• noun The rock-rose or sun-rose. See Helianthemum.
• noun The marigold, Calendula officinalis, from its opening and closing with the ascent and descent of the sun.
• noun In civil engineering, a full-circle protractor arranged for vertical mounting on a tripod.
• noun In writing-telegraphs and other electrical instruments and apparatus, a series of alternate conducting and insulating segmental pieces or tablets symmetrically arranged in circular form, each conducting piece being connected with a source of electricity and also with the ground.

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

• noun Any plant of the genus Helianthus; -- so called probably from the form and color of its flower, which is large disk with yellow rays. The commonly cultivated sunflower is Helianthus annuus, a native of America.

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

• noun Any plant of the genus Helianthus, so called probably from the form and color of its floral head, having the form of a large disk surrounded by yellow ray flowers; the commonly cultivated sunflower is Helianthus annuus, a native of America.
• noun colour a bright yellow, like that of the flower petals.

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

• noun any plant of the genus Helianthus having large flower heads with dark disk florets and showy yellow rays