Humin

from WordNet (r) 3.0 (2006)
humin
    n 1: a black humic substance that is not soluble in water
    
from The Collaborative International Dictionary of English v.0.48
Humin \Hu"min\, n. [L. humus the earth, ground.] (Chem.)
   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.
   [1913 Webster]
    

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