1. (grĕnĭch, grĭnĭj) A borough of Greater London in southeast England on the Thames River. It is the site of the original Royal Observatory, through which passes the Prime Meridian, or longitude 0°.
2. (grĕnĭch, grĭn-, grēnwĭch′) A town of southwest Connecticut on Long Island Sound. Settled in 1640, it is a wealthy suburb of New York City and home to many investment companies.