hackberry

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

• noun Any of various trees or shrubs of the genus Celtis, having inconspicuous flowers and small, usually ovoid drupes.
• noun The fruit of such a plant.
• noun The soft yellowish wood of any of these trees or shrubs.

from The Century Dictionary.

• noun Same as hagberry. Also called bird-cherry.
• noun An American tree, Celtis occidentalis, natural order Urticaceæ, allied to the elm. It ranges from Canada to Florida and west to Texas, but is most typical and abundant in the Mississippi valley.

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

• noun (Bot.) A genus of trees (Celtis) related to the elm, but bearing drupes with scanty, but often edible, pulp. Celtis occidentalis is common in the Eastern United States.

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

• noun Any of several small shrubs or trees of the genus Celtis, having small fruit.
• noun The purple-black fruit of such plants.
• noun uncountable The soft wood of such plants.

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

• noun any of various trees of the genus Celtis having inconspicuous flowers and small berrylike fruits
• noun small edible dark purple to black berry with large pits; southern United States