buckeye

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

• noun Any of several North American trees or shrubs of the genus Aesculus, having palmately compound leaves, erect panicles of white, yellow, or red flowers, and a leathery capsule containing one or more large seeds. All parts of the plant are poisonous.
• noun The large shiny brown seed of any of these plants.
• noun A nymphalid butterfly (Junonia coenia) of North America, having brownish wings with orange markings and conspicuous eyespots.

from The Century Dictionary.

• noun An American name for the different species of horse-chestnut, Æsculus, native to the United States.
• noun An inhabitant of Ohio, which is often called the Buckeye State, from the great number of horse-chestnuts in it.
• noun A flat-bottomed centerboard schooner of small size (3 to 15 tons), decked over, and with a cabin aft, used in oyster-fishing in Chesapeake Bay. Also called bugeye.
• noun In entomology, an American nymphalid butterfly, Junonia cœnia.

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

• noun (Bot.) A name given to several American trees and shrubs of the same genus (Æsculus) as the horse chestnut.
• noun is Aesculus glabra.
• noun is Aesculus Pavia.
• noun is Aesculus paviflora.
• noun is Aesculus flava.
• noun U.S. A cant name for a native or resident of Ohio.
• noun Ohio; -- so called because buckeye trees abound there.

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

• noun Any of several species of trees, of the genus Aesculus, or the related Mexican Buckeye (genus Ungnadia).
• noun The seed or fruit of these plants
• noun A native or resident of the American State of Ohio.

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

• noun tree having palmate leaves and large clusters of white to red flowers followed by brown shiny inedible seeds
• noun the inedible nutlike seed of the horse chestnut
• noun a native or resident of Ohio