obumbrate

from The Collaborative International Dictionary of English v.0.48

Obumbrate \Ob*um"brate\, v. t. [L. obumbratus, p. p. of
   obumbrare to overshadow, cloud; ob + umbrare to shade.]
   To shade; to darken; to cloud. [R.] --Howell.
   [1913 Webster]