n. The wood nearer the heart of a stem or branch, different in color from the sapwood
the GNU version of the Collaborative International Dictionary of English
n. The hard, central part of the trunk of a tree, consisting of the old and matured wood, and usually differing in color from the outer layers. It is technically known as duramen, and distinguished from the softer sapwood or alburnum.
The Century Dictionary and Cyclopedia
n. The central wood in the trunk of an exogenous tree; duramen.
n. The Tasmanian ironwood, Notelæa ligustrina, the hard, close-grained wood of which is used for turning.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the older inactive central wood of a tree or woody plant; usually darker and denser than the surrounding sapwood
Word Usage
"Fortunately, he accepted me as his Ph.D. student and I began to explore the neoflavonoids found in a piece of heartwood from a Brazilian tree."