The phrase "floating on air" is commonly used to describe a feeling of extreme happiness or elation. Its antonyms would be words that describe the opposite feeling, such as despair, sadness, or depression. Some antonyms for "floating on air" include: being weighed down, feeling grounded, feeling down or depressed, feeling blue or unhappy, feeling heavyhearted or discouraged. It is important to note that while these antonyms may be used to describe the opposite of "floating on air," they do not necessarily mean that the individual is experiencing a negative emotion. Everyone experiences highs and lows, and it is perfectly normal to feel a range of emotions.