The word "knuckleheaded" is an informal, slang term that means foolish or stupid. Antonyms, or words that have the opposite meaning of knuckleheaded, include intelligent, clever, wise, astute, bright, and sensible. Words like sharp-witted, shrewd, perceptive, and discerning can also be used to describe the opposite of a knuckleheaded person. Antonyms are a great way to expand your vocabulary and improve your communication skills. By using the right antonym, you can clearly express your ideas and convey your message effectively, avoiding confusion and misunderstandings. So, the next time you come across the word knuckleheaded, think of its antonyms and choose the right word to use in its place.