Source : Webster's Revised Unabridged Dictionary (1913)

Thready \Thread"y\, a.
   1. Like thread or filaments; slender; as, the thready roots
      of a shrub.

   2. Containing, or consisting of, thread.

Source : WordNet®

thready
     adj 1: forming viscous or glutinous threads [syn: {ropy}, {ropey},
            {stringy}]
     2: thin in diameter; resembling a thread [syn: {filamentous}, {filiform},
         {filamentlike}, {threadlike}]
     [also: {threadiest}, {threadier}]