In a bleating manner; with a characteristic bleating sound or in a whining, complaining way.
From bleat + -ing (present participle) + -ly (adverb suffix). This triple-suffix construction is productive in English, allowing us to turn simple verbs into descriptive adverbs with precise meaning.
Words ending in -ingly are relatively rare and formal-sounding, which is why adding it to 'bleating' makes the description feel more literary and exaggerated—perfect for dramatic writing about someone's annoying whining.
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