Most airheaded, meaning foolish or lacking intelligence, can have many antonyms. One antonym could be intelligent, implying that the person or thing in question is very smart or shrewd. Another antonym could be astute, suggesting that the person is perceptive or insightful. A third antonym could be wise, which refers to someone with great knowledge, judgment, or experience. Other antonyms for most airheaded might include insightful, brilliant, genius, bright, and clever. In essence, the antonyms for most airheaded all have one thing in common: they imply a level of intelligence or shrewdness that is the exact opposite of foolishness.