Generally used in informal speech and not in formal writing or professional settings. Stop being a windbag and get to the point!
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Negative Connotation
'Windbag' is usually used to criticize someone's speaking style as annoying or excessive. I couldn't get a word in with that windbag monopolizing the conversation.
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Slang Alternatives
Similar informal slang includes 'gasbag' or 'blabbermouth' with the same negative implication. He's such a gasbag at parties, just like an old windbag at family gatherings.