Bosporus

n. strait which separates the Asian and European parts of Turkey, strait which connects the Black Sea to the Marmara Sea

The Bosporus or Bosphorus, also known as the Istanbul Strait, (Turkish: İstanbul Boğazı) (Greek: Βόσπορος) is a strait that forms the boundary between the European part (Rumelia) of Turkey and its Asian part (Anatolia). The world's narrowest strait used for international navigation, it connects the Black Sea with the Sea of Marmara (which is connected by the Dardanelles to the Aegean Sea, and thereby to the Mediterranean Sea). It is approximately 30 km long, with a maximum width of 3,700 metres at the northern entrance, and a minimum width of 700 metres between Kandilli and Aşiyan; and 750 metres between Anadoluhisarı and Rumelihisarı. The depth varies from 36 to 124 metres in midstream.
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Noun
1. a strait connecting the Mediterranean and the Black Sea; separates the European and Asian parts of Turkey; an important shipping route
(hypernym) strait, sound
(part-holonym) Turkey, Republic of Turkey

n. Bosporus, strait dividing the Asian and European portion of Turkey

(n.)
A strait or narrow sea between two seas, or a lake and a seas; as, the Bosporus (formerly the Thracian Bosporus) or Strait of Constantinople, between the Black Sea and Sea of Marmora; the Cimmerian Bosporus, between the Black Sea and Sea of Azof.