In a bustling manner; with busy, energetic, purposeful activity and constant motion.
From 'bustling' (present participle of bustle, meaning actively busy) plus adverbial suffix '-ly'; creates an adverb describing the manner or way in which bustling occurs.
Adverbs like 'bustlingly' are wonderfully Victorian constructions—imagine a narrator describing the 'bustlingly efficient' household manager, making a quality of movement into a moral virtue.
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