To puff up is to swell out, or to make somebody conceited. The bird puffed up against the cold.
Birds puff up to trap air in the feathers, which is why they look twice the size in winter. To puff up a person is what praise does when there is too much of it.
1phrasepuff upTo swell out, or to make somebody conceited.
“The sparrows would puff up until they were nearly round.”
puff up is a phrase.
Practised in A Song of Ice and Fire