(formerly) the mainland of America adjacent to the Caribbean Sea, especially the area between the mouth of the Orinoco River and the Isthmus of Panama.
the Caribbean Sea: the route of the Spanish treasure galleons and a former haunt of pirates.
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British Dictionary definitions for spanish main
the mainland of Spanish America, esp the N coast of South America from the Isthmus of Panama to the mouth of the Orinoco River, Venezuela
the Caribbean Sea, the S part of which in colonial times was the route of Spanish treasure galleons and the haunt of pirates
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012