Lunkheaded is defined as being slow-witted, dim or foolish. Antonyms, on the other hand, are words that mean the opposite to a particular word. Some possible antonyms for lunkheaded may include intelligent, astute or sharp-witted. Other antonyms could be brainy, bright or clever. Additionally, quick-witted, smart, sharp or quick-thinking could be considered antonyms for lunkheaded. The opposite of being foolish or thick-headed is being wise, knowledgeable or shrewd. Overall, there are many different antonyms which could be used to describe the opposite of lunkheaded.