Source : Webster's Revised Unabridged Dictionary (1913)

Filamentous \Fil`a*men"tous\, a. [Cf. F. filamenteux.]
   Like a thread; consisting of threads or filaments. --Gray.

Source : WordNet®

filamentous
     adj : thin in diameter; resembling a thread [syn: {filiform}, {filamentlike},
            {threadlike}, {thready}]