"Puffing up" is a phrase that means to swell or expand in size. It can be used in a variety of contexts, such as describing a balloon filling with air or a person's ego becoming inflated. Some synonyms for "puffing up" include swelling, bloating, inflating, expanding, distending, and enlarging. These words all convey the idea of something increasing in size, whether it's a physical or abstract concept. Additionally, some synonyms for "puffing up" that relate specifically to ego or attitude include boasting, bragging, and exaggerating. These words suggest an overinflated sense of self-importance, which can lead to negative consequences.