The Collaborative International Dictionary of English v.0.48:

Tendril \Ten"dril\, n. [Shortened fr. OF. tendrillon, fr. F.
   tendre tender; hence, properly, the tender branch or spring
   of a plant: cf. F. tendrille. See Tender, a., and cf.
   Tendron.] (Bot.)
   A slender, leafless portion of a plant by which it becomes
   attached to a supporting body, after which the tendril
   usually contracts by coiling spirally.
   [1913 Webster]

   Note: Tendrils may represent the end of a stem, as in the
         grapevine; an axillary branch, as in the passion
         flower; stipules, as in the genus Smilax; or the end of
         a leaf, as in the pea.
         [1913 Webster]
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tendril \Ten"dril\, a.
   Clasping; climbing as a tendril. [R.] --Dyer.
   [1913 Webster] Tendriled

WordNet (r) 3.0 (2006):

tendril
    n 1: slender stem-like structure by which some twining plants
         attach themselves to an object for support