Thick-headed is an adjective used to describe someone who is dull-witted, slow, or stubborn. The antonyms for "thick-headed" include words like "sharp," "clever," "bright," "smart," or "intelligent." By using these words, we can show that the opposite of being thick-headed is to be quick, insightful or witty. Additionally, the antonyms for "thick-headed" can also include words like "sensible", "pragmatic", or "reasonable". These words indicate that someone who is not thick-headed is capable of understanding situations and making sound decisions. Using antonyms can help add depth and nuance to our language as we strive to express ourselves with precision and clarity.