The antonym for dissimulate is "reveal" which means to make known something previously secret or unknown, to disclose or uncover. Another antonym might be "honestly" which refers to the truthful and straightforward communication of one's thoughts, feelings and intentions. When someone is honest, they speak and act with authenticity, without any pretense or concealment. A third antonym could be "clarify" which means to make something easier to understand or to remove any ambiguities or confusion that might exist. When we clarify our intentions or actions, we help others to better understand and relate to us, thus avoiding any potential misunderstandings.