The Collaborative International Dictionary of English v.0.48:

filiform \fil"i*form\, a. [L. filum thread + -form: cf. F.
   filiforme.]
   Having the shape of a thread or filament; as, the filiform
   papill[ae] of the tongue; a filiform style or peduncle. See
   Illust. of Antenn[ae].
   [1913 Webster] Filigrain

WordNet (r) 3.0 (2006):

filiform
    adj 1: thin in diameter; resembling a thread [syn:
           filamentous, filiform, filamentlike, threadlike,
           thready]