Bullet-headed is an adjective that refers to someone who has a large, round head that is often compared to a bullet in shape. There are several synonyms for bullet-headed, including blockheaded, thick-headed, and knuckleheaded. Each of these synonyms describes someone who is dense or obtuse in their thinking or behaviors. Other synonyms include pot-headed, a slang term used to describe someone who is habitually intoxicated and has a swollen head, and dome-headed, which refers to someone who has a large, bulging forehead. While these synonyms may not be appropriate in all situations, they can be useful in describing someone with a certain type of appearance or demeanor.