~ 1
■ noun a place where birds regularly settle to rest at night, or where bats congregate to rest in the day.
■ verb (of a bird or bat) settle or congregate for rest.
Origin
OE hrōst ; of unknown ultimate origin.
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~ 2
■ noun (in the Orkneys and Shetlands) a tidal race.
Origin
C17: from ON rỏst .