The Collaborative International Dictionary of English v.0.48:

Incogitant \In*cog"i*tant\, a. [L. incogitans; pref. in- not +
   cogitans, p. pr. of cogitare to think. See Cogitate.]
   Thoughtless; inconsiderate. [R.] --Milton.
   [1913 Webster]

         Men are careless and incogitant.         --J. Goodman.
   [1913 Webster]