Region: General | Usage example: Ignore him; he's full of hot air when he promises miracles.

Full of hot air

Meaning

Talkative without substance.

Used to call out empty boasting.

Origin notes can vary by region and source; this page gives the commonly reported explanation and usage context.

Hot air is light and insubstantial, like boastful speech.

English slang from the early 20th century.