Gulf of Finland

n. eastern arm of the Baltic Sea located between Finland and Estonia and Russia

The Gulf of Finland is an arm of the Baltic Sea that extends between Finland (to the north) and Estonia (to the south) all the way to the city of Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn.
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Noun
1. an eastern arm of the Baltic Sea; between Finland and Estonia
(hypernym) gulf
(part-holonym) Baltic, Baltic Sea