Source : Webster's Revised Unabridged Dictionary (1913)

Cretinous \Cre"tin*ous\ (-[u^]s), a.
   Having the characteristics of a cretin. ``Cretinous
   stupefaction.'' --Ruskin.

Source : WordNet®

cretinous
     adj 1: affected with or resembling cretinism; "cretinous
            development"
     2: afflicted with cretinism