Kui·per belt 
(kīpər)
(kīpər)n.
A disk-shaped region in the outer solar system lying beyond the orbit of Neptune and extending to a distance of about 50 astronomical units, containing thousands of small icy bodies, some of which are on highly elliptical orbits, periodically visiting the inner solar system as comets.
[After Gerard Kuiper (1905-1973), Dutch-born American astronomer who speculated about the existence of such a region.]