To surge, boil, or surge back and forth like a tide (archaic); to flow with an ebbing and flowing motion.
From Latin 'aestuare' (to surge, boil, heave). The same root as 'estuary' and 'estuant,' preserving the original meaning of tidal motion.
This forgotten verb perfectly captures what tides do—they don't just rise or fall, they surge and push back and forth—and the Romans had one elegant word for that rhythmic, agitated movement.
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