A person who speaks or writes in a pompous, exaggerated, or inflated manner without substance.
From 'bombast' (pompous language) plus the agent suffix '-er'. 'Bombast' itself comes from 'bombace' (cotton padding), metaphorically describing speech 'padded' with air.
Bombaster comes from cotton stuffing—people noticed that overblown speech was like clothing stuffed with padding: lots of volume but nothing solid underneath!
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