THESAURUS
knuckleheaded
beetleheaded, blockheaded, blunderheaded, boneheaded, cabbageheaded, chowderheaded, chuckleheaded, clodpated, dumbheaded, dunderheaded, fatheaded, jolterheaded, joltheaded, lunkheaded, muttonheaded, nitwitted, numskulled, pumpkin-headed, sapheaded, stupidheaded, woodenheaded