Undissimulating is a word that is used to describe someone who is honest and straightforward in their actions and words. If you're looking for synonyms for this word, you might consider using terms like genuine, sincere, forthright, straightforward, transparent, frank, open, candid, truthful, and honest. These words all suggest a lack of deception or pretense and convey a sense of honesty and integrity. Using these synonyms in your writing or speech can help you convey the same sense of trustworthiness and straightforwardness that the word "undissimulating" implies.