Antonyms are words that are opposite in meaning to another word. For the phrase "rate highly," some antonyms might include "disparage," "criticize," "devalue," or "diminish." These words indicate a negative attitude toward the subject being evaluated, and they suggest that the person doing the rating does not think very highly of it. As a writer or speaker, selecting the right antonyms can help you convey a wide range of attitudes and opinions. By choosing the right words, you can create a more complex and nuanced response to a given topic, adding depth and interest to your communication.