WordNet sense 1 (devoid of intelligence):

asinine, fatuous, inane, vacuous

WordNet sense 2 (devoid of good sense or judgment):

foolish

WordNet sense 3 (not mindful or attentive):

forgetful, unmindful

WordNet sense 4 (not marked by the use of reason):

senseless, reasonless

WordNet sense 5 (not reasonable; not showing good judgment):

unreasonable

WordNet sense 6 (having no meaning or direction or purpose):

meaningless, nonmeaningful

WordNet sense 7 (not intellectual):

nonintellectual