The antonyms for the term "be pertinent" are several. Words like irrelevant, unrelated, impertinent, immaterial, insignificant, and unimportant are the opposite of the word pertinent. In other words, these words are used to denote something that is not related to the issue at hand, does not add any value or is completely irrelevant. For example, when discussing the benefits of a vegetarian diet, discussing the latest fashion trends would be irrelevant. Similarly, talking about your favorite music band during a business meeting is immaterial and unimportant. Therefore, it is essential to be mindful of the context when using words like pertinent and their antonyms.