lackadaisical

lackadaisical \lack-uh-DAY-zih-kuhl\, adjective:

Lacking spirit or liveliness; showing lack of interest; languid; listless.

Drowsy from the heat and from fatigue, he dozed to the steady lackadaisical clips of the mule's shoes.
-- Patricia Powell, The Pagoda

There was an oddly lackadaisical inflection to his speech. A sense of merely going though the motions.
-- Lesley Hazleton, Driving To Detroit

The very title, Hours of Idleness, which the young lord affixed to his maiden volume, sufficiently indicated the lackadaisical spirit in which he came before the public.
-- J. F. A. Pyre, "Byron in Our Day", The Atlantic, April 1907

The simple fact is, whether we admit it or not, there's never been an "intelligence" or "achievement" test on which the smart and industrious have not done better than the dumb and the lackadaisical.
-- Jonah Goldberg, "Stupid Aptitude Test", National Review, July 1, 2002

Lackadaisical comes from the expression lackadaisy, a variation of lackaday, itself a shortening of "alack the (or a) day!"