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Prate
Negative Connotation
Indicates useless talk; often has a negative undertone, suggesting the speaker's words are wasteful. 
Verb Form
'Prate' is a verb; you can't 'be' prate or 'have' prate, you can only 'prate about' something. 
Casual Context
Commonly used in informal situations, not usually found in formal writing or speech. 