water elm

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

• noun A small deciduous elmlike tree (Planera aquatica) of wetlands of the southeast United States, having small nutlike fruit with irregular fleshy projections.

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

• noun large ornamental tree with graceful gradually spreading branches common in eastern North America
• noun Eurasian elm closely resembling the American elm; thrives in a moist environment