Green ‧ wich /ˈɡrenɪtʃ, ˈɡrɪnɪdʒ/ BrE AmE
an area of southeast London on the River Thames. The original British Royal ↑ observatory (=a special building from which scientists watch the moon, stars etc) is there, and the 0°↑ meridian (=an imaginary line which divides the eastern and western halves of the world) passes through the grounds of the Observatory.