The antonyms for the phrase "feeling up" can mean different things depending on the context. In a negative context, antonyms for feeling up are feeling down, being depressed, and feeling low. They mean the opposite of being joyful and confident. In a physical context, feeling up can mean assessing or examining something, and the antonyms include ignoring, neglecting, and avoiding. Thus, the antonyms for feeling up can vary depending on the context and the meaning behind the phrase. It is important to understand the correct usage of antonyms to avoid confusion and misunderstandings.