The word "unmask" refers to the act of revealing or exposing something that was previously kept hidden or secret. Antonyms for this word would include words that describe actions or states that involve concealment or secrecy, such as cover, cloak, hide, disguise, or mask. These antonyms indicate actions or states that prevent one from seeing or knowing the truth, or from being able to discern what is really happening. Thus, while "unmask" implies an act of truth-telling or revelation, its antonyms suggest a lack of transparency, openness, or honesty.