n. The part of the organic matter in soil that does not dissolve in dilute alkali
the GNU version of the Collaborative International Dictionary of English
n. A bitter, brownish yellow, amorphous substance, extracted from vegetable mold, and also produced by the action of acids on certain sugars and carbohydrates; -- called also humic acid, ulmin, gein, ulmic or geic acid, etc.
The Century Dictionary and Cyclopedia
n. A neutral indifferent substance said by Mulder to exist in black humus.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a black humic substance that is not soluble in water