Source : Webster's Revised Unabridged Dictionary (1913)

Tomentum \To*men"tum\, n.; pl. {Tomenta}. [L. See {Tomentose}. ]
   (Bot.)
   The closely matted hair or downy nap covering the leaves or
   stems of some plants.

Source : WordNet®

tomentum
     n 1: filamentous hairlike growth on a plant; "peach fuzz" [syn: {hair},
           {fuzz}]
     2: a network of tiny blood vessels between the cerebral surface
        of the pia mater and the cerebral cortex [syn: {tomentum
        cerebri}]
     [also: {tomenta} (pl)]