1) Syrtis, the name of two places in the African or Libyan Sea between Carthage and Cyrenaicia, full of shallows and sandbanks, and therefore destructive to ships; the western Syrtis, between the islands Cercina and Meninx (or the promontories of Zeitha and Brachodes), was called Syris minor, the eastern (extending from the promontories of Cephalae on the west to that of Boreum on the east) was called Syris major; this latter must be the one referred to in Act 27:17, for upon this the ship in which Paul was sailing might easily be cast after leaving Crete
Part of Speech: noun proper feminine
From G4951; a shoal (from the sand drawn thither by the waves), that is, the Syrtis Major or great bay on the North coast of Africa: - quicksands.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root Σύρτις; click on the second column to search for that grammatical form of the root Σύρτις; click on the third column to search for that word and grammatical form; click on the total to search for the root Σύρτις.