In a manner that is very old, worn-out, weak, or showing signs of age and decay.
From 'decrepit' (very old and worn out) plus the adverb suffix '-ly.' This adverb form allows the adjective to modify verbs and other adjectives.
When something moves 'decrepitly'—like an ancient, creaky wooden bridge or an elderly person walking slowly—the word itself sounds as frail as its meaning!
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