The phrase "biggest icebergs" refers to the largest pieces of ice that have broken away from glaciers or ice shelves and are floating in the ocean. These icebergs can be massive in size and can pose risks to ships and ecosystems. Full definition
Big icebergs break off Antarctica naturally, meaning scientists are not linking the rift to manmade climate change. (scientificamerican.com)
He side - stepped Maddow's question on whether he sympathizes with the Occupy Wall Streeters protesting right across the street from his Lower Manhattan office in Zuccotti Park, although he did say that he thought these demonstrations are merely «the tip of a much bigger iceberg» and proof that Americans are generally angry and dissatisfied with the government. (nystateofpolitics.com)