|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison.|
third nearest of the five major moons of Uranus and the one having the darkest and oldest surface of the group. Its discovery is attributed to the English astronomer William Lassell in 1851, although the English astronomer William Herschel, who discovered Uranus and its two largest moons, may have glimpsed it more than a half century earlier. Umbriel was named by Herschel's son, John, for a character in Alexander Pope's poem The Rape of the Lock
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