A.Word.A.Day -- hebetudinous:

hebetudinous (heb-i-TOOD-n-uhs -TYOOD-) adjective

Dull or lethargic, especially relating to the mind.

[From Late Latin hebetudo (dullness), from Latin hebes (dull).]

“Examination of precedents led the judge to his conclusion, but he had something to say first: 'It would be hebetudinous and obtuse to fail to be cognizant of the adverse consequences of a ruling in this case.” James J. Kilpatrick; A Clown And a Blowhard on the Bench; Buffalo News; Apr 10, 1993.