Happening in sudden bursts or starts and stops rather than continuously; not steady or regular.
From 'fit' (a sudden attack or episode) plus '-ful' (full of), dating to the 1600s. Originally related to seizures or sudden physical episodes, then broadened to mean any irregular pattern.
We still use 'fitful sleep' to describe restless nights because the word perfectly captures that stop-start feeling—your eyes open, close, open again, never settling into deep rest.
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