The phrase "be source of" refers to being the origin or cause of something. Its antonyms would be terms such as "stop," "prevent," "halt," or "bring to an end." These words indicate actions that would impede or cease the cause of something. Alternatively, antonyms could also be terms such as "receive," "adopt," "accept," or "yield." These words indicate actions that do not result in the origin of something, but rather welcome or receive an effect. It is important to understand antonyms in order to use them effectively in speech or writing, as they can greatly alter the meaning of a sentence or phrase.