Source : Webster's Revised Unabridged Dictionary (1913)

Dopey \Dop"ey\, a.
   Affected by ``dope''; esp., sluggish or dull as though under
   the influence of a narcotic. [Slang]

Source : WordNet®

dopey
     adj : having or revealing stupidity; "ridiculous anserine
           behavior"; "a dopey answer"; "a dopey kid"; "some fool
           idea about rewriting authors' books" [syn: {anserine},
           {dopy}, {foolish}, {goosey}, {goosy}, {gooselike}]
     [also: {dopiest}, {dopier}]