'Geode' definitions:

Definition of 'geode'

(from WordNet)
noun
(mineralogy) a hollow rock or nodule with the cavity usually lined with crystals

Definition of 'Geode'

From: GCIDE
  • Geode \Ge"ode\ (j[=e]"[=o]d), n. [F. g['e]ode, L. geodes, fr. Gr. ? earthlike; ge`a, gh^, the earth + e'i^dos form.] (Min.) (a) A nodule of stone, containing a cavity, lined with crystals or mineral matter. (b) The cavity in such a nodule. [1913 Webster]