WordNet sense 1 (devoid of intelligence):

asinine, fatuous, inane, mindless

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

foolish

WordNet sense 3 (devoid of significance or point):

hollow

WordNet sense 4 (having no meaning or direction or purpose):

meaningless, nonmeaningful

WordNet sense 5 (holding or containing nothing):

empty

WordNet sense 6 (void of expression):

blank

WordNet sense 7 (not inclined to talk or give information or express opinions):

uncommunicative, incommunicative