The phrase "most sub-rosa" is an idiom that means something is happening secretly, confidentially, or privately. It implies that whatever is occurring is hidden, covert, or clandestine. Therefore, some of the antonyms that can replace this phrase are openness, transparency, honesty, and publicity. These words denote the opposite meaning of discreetness or secrecy. They signify that things are open, visible, and accessible to the public. Hence, they connote free flow of information, lack of concealment, and straightforwardness. Using appropriate antonyms can help to create a more precise and accurate description, depending on the context in which the term "most sub-rosa" is used.