Nontransparent refers to something that is not clear or open about its actions or intentions. The antonyms for nontransparent are words that describe clarity, openness, and honesty. These words include transparent, clear, open, honest, sincere, forthright, frank, candid, and straightforward. Transparent refers to something that is clear and easily understood. Clear describes something that is easy to see or understand. Open refers to something that is not hidden or secretive. Honest, sincere, forthright, frank, and candid all describe people who are open and truthful in their dealings. Lastly, straightforward refers to something that is free from ambiguity or confusion. These antonyms all emphasize the importance of clarity, honesty, and openness in communication and decision-making.