Long Island UK /ˌlɒŋ ˈaɪlənd/US /ˌlɔŋ ˈaɪlənd/ noun3 •The biggest and longest island of the contiguous United States, located in the state of New York. •region of New York state consisting of Nassau County and Suffolk County, to the exclusion of Brooklyn and Queens (the parts of the island found in New York City).After receiving a $2 million investment on the show, the company moved its headquarters from Queens to Long Island. — 2017 •(informal) A Long Island iced tea. formsLong Islands