The Collaborative International Dictionary of English v.0.48:

Plumbean \Plum"be*an\, Plumbeous \Plum"be*ous\, a. [L. plumbeus,
   from plumbum the metal lead.]
   1. Consisting of, or resembling, lead. --J. Ellis.
      [1913 Webster]

   2. Dull; heavy; stupid. [R.] --J. P. Smith.
      [1913 Webster]