Unmysterious is a word used to describe something that is plain or straightforward. Antonyms for this word, on the other hand, can be used to describe things that are enigmatic, incomprehensible, or perplexing. The opposite of being plain, around being mysterious, is shrouded. Antonyms for unmysterious could include words such as mysterious, abstruse, obscure, or puzzling. These words suggest that something is cloaked in secrecy or hidden from view, making it difficult to understand. The antonyms for unmysterious can help to create a sense of wonder, intrigue or mystique, adding an element of complexity to the world around us.