The Collaborative International Dictionary of English v.0.48:

Plethoric \Ple*thor"ic\, a. [Gr. ?; cf. F. pl['e]thorique.]
   Haeving a full habit of body; characterized by plethora or
   excess of blood; as, a plethoric constitution; -- used also
   metaphorically. "Plethoric phrases." --Sydney Smith.
   "Plethoric fullness of thought." --De Quincey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

plethoric
    adj 1: excessively abundant [syn: overabundant, plethoric,
           rife]