Source : Webster's Revised Unabridged Dictionary (1913)

Radicle \Rad"i*cle\, n. [L. radicula, dim. of radix, -icis,
   root: cf. F. radicule. See {Radix}.] (Bot.)
   (a) The rudimentary stem of a plant which supports the
       cotyledons in the seed, and from which the root is
       developed downward; the stem of the embryo; the caulicle.
   (b) A rootlet; a radicel.

Source : WordNet®

radicle
     n : (anatomy) a small structure resembling a rootlet (such as a
         fibril of a nerve)