water lily

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

• noun Any of various ornamental aquatic plants of the family Nymphaeaceae and especially of the genera Nymphaea and Nuphar, having large floating leaves and showy, variously colored flowers.

from The Century Dictionary.

• noun A plant of the genus Castalia (Nymphæa), which contains about 25 species distributed nearly throughout the world, but most freely in the northern hemisphere and the tropics.
• noun The pond-lily, or yellow water-lily, Nymphæa (Nuphar) lutea. See pond-lily.
• noun In general, any plant of the order Nymphæaceæ, the water-lily family. See the phrases below.

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

• (Bot.) A blossom or plant of any species of the genus Nymphæa, distinguished for its large floating leaves and beautiful flowers. See nymphæa.

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

• noun botany Any of various members of the Nymphaeaceae family that are tuberous plants, rooted in soil with leaves and flowers floating on the water surface.

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

• noun an aquatic plant of the family Nymphaeaceae