The Collaborative International Dictionary of English v.0.48:

Infuscate \In*fus"cate\, v. t. [L. infuscatus, p. p. of
   infuscare; pref. in- in + fuscare to make dark, fr. fuscus
   dark.]
   To darken; to make black; to obscure.
   [1913 Webster]

WordNet (r) 3.0 (2006):

infuscate
    v 1: darken with a brownish tinge, as of insect wings