Bosporus \Bos"po*rus\ (b[o^]s"p[-o]*r[u^]s), n. [L.]

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. [Written also Bosphorus.]

Source: Webster's Revised Unabridged Dictionary (1913)