"Muddled-thinking" is the antonym for clear-thinking. A muddled thinker is someone who has difficulty organizing their thoughts, lacks clarity, and may be easily overwhelmed by complex or abstract concepts. They often struggle to make decisions and may be prone to second-guessing themselves. Other antonyms for clear-thinking could include "confused," "obscured," "unclear," "jumbled," or "disorganized." These words all suggest a lack of mental clarity and an inability to process information effectively. Clear-thinking is essential for success in academic or professional settings, whereas muddled-thinking can lead to poor decision-making, misunderstandings, and confusion.