In a manner characterized by fluttering movements or a fluttering quality; with quick, trembling, or unsteady motions.
From flutter + -ing (present participle) + -ly (adverb suffix). The -ly suffix transforms the participle into an adverb describing how an action is performed.
Adverbs like this one show how English builds descriptive complexity—instead of saying 'in a fluttering way,' we compact it into one elegant word that paints a vivid picture of movement.
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