Dehortatory is a rare word that describes something that dissuades or discourages. If you're looking for a synonym for this word, there are several options that you can consider. Some possible substitutes for dehortatory include admonitory, dissuasive, discouraging, disheartening, negative, warning, and inhibitive. All of these words convey a sense of discouragement or advice against doing something. So if you're trying to describe a speech or action that is meant to discourage someone from taking a certain course, any of these alternatives to dehortatory would be appropriate to use.