puff up
Definitions
To swell or become larger, typically due to air, fluid, or inflammation.
To become inflated with pride, arrogance, or self-importance.
To expand in size or volume, often referring to baked goods rising in an oven.
Examples
The angry cat began to puff up its fur to appear larger to the intruder.
You should puff up the pillows on the sofa to make the living room look more inviting.