The Collaborative International Dictionary of English v.0.48:

Scion \Sci"on\, n. [OF. cion, F. scion, probably from scier to
   saw, fr. L. secare to cut. Cf. Section.]
   1. (Bot.)
      (a) A shoot or sprout of a plant; a sucker.
      (b) A piece of a slender branch or twig cut for grafting.
          [Formerly written also cion, and cyon.]
          [1913 Webster]

   2. Hence, a descendant; an heir; as, a scion of a royal
      stock.
      [1913 Webster]

WordNet (r) 3.0 (2006):

scion
    n 1: a descendent or heir; "a scion of royal stock"