[ moon ]
/ mun /
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verb (used without object)
verb (used with object)
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Idioms about moon

    blue moon. See entry at blue moon.
    over the moon. See entry at over the moon.

Origin of moon

before 900; Middle English mone,Old English mōna; cognate with Old High German māno,Old Norse māni,Gothic mena; akin to German Mond moon, Latin mēnsis month, Greek mḗnē moon, Sanskrit māsa moon, month


moon·er, nounmoon·less, adjective

Other definitions for moon (2 of 2)

[ moon ]
/ mun /

Sun Myung [suhn myuhng], /sʌn myʌŋ/, 1920–2012, Korean religious leader: founder of the Unification Church.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use moon in a sentence

British Dictionary definitions for moon (1 of 3)

/ (muːn) /

(when tr, often foll by away; when intr, often foll by around) to be idle in a listless way, as if in love, or to idle (time) away
(intr) slang to expose one's buttocks to passers-by

Derived forms of moon

moonless, adjective

Word Origin for moon

Old English mōna; compare Old Frisian mōna, Old High German māno

British Dictionary definitions for moon (2 of 3)

/ (muːn) /

a system of embossed alphabetical signs for blind readers, the fourteen basic characters of which can, by rotation, mimic most of the letters of the Roman alphabet, thereby making learning easier for those who learned to read before going blindCompare Braille 1

British Dictionary definitions for moon (3 of 3)

/ (muːn) /

William. 1818–94, British inventor of the Moon writing system in 1847, who, himself blind, taught blind children in Brighton and printed mainly religious works from stereotyped plates of his own designing
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for moon

[ mōōn ]

Often Moon. The natural satellite of Earth, visible by reflection of sunlight and traveling around Earth in a slightly elliptical orbit at an average distance of about 381,600 km (237,000 mi). The Moon's average diameter is 3,480 km (2,160 mi), and its mass is about 180 that of Earth. Its average period of revolution around Earth is 29 days, 12 hours, 44 minutes. See more at giant impact theory.
A natural satellite revolving around a planet.

A Closer Look

The Earth's Moon is a desolate and quiet place. The only natural satellite of Earth, it consists almost entirely of rock, shows no signs of ongoing geologic activity, has no water, and has a very thin atmosphere consisting primarily of sodium. But our Moon does not present a typical case for planetary satellites. Over the last 50 years, over a hundred more moons have been discovered in the solar system, so that they now total 165, nearly all of them orbiting the larger planets Jupiter, Saturn, and Uranus (Mercury and Venus have no moon), with an additional four moons orbiting dwarf planets. Because they are so far from the Sun, these moons are for the most part extremely cold. Io, one of Jupiter's 63 known moons, is an exception. It is the most geologically active body in the solar system, with almost constant volcanic activity and a surface covered by cooling lava. Some scientists think that another moon of Jupiter, Europa, may have liquid water capable of supporting life underneath a thick layer of surface ice. Titan, one of Saturn's moons, may also be capable of supporting primitive life in the ocean of liquid methane on its frigid surface.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for moon


A natural satellite of a planet; an object that revolves around a planet. The planets vary in the number of their moons; for example, Mercury and Venus have none, the Earth has one, and Jupiter has seventeen or more. The planets' moons, like the planets themselves, shine by reflected light.

notes for moon

The Earth's moon is about 240,000 miles away and is about 2,000 miles in diameter. The volume of the Earth is fifty times that of the moon; the mass of the Earth is about eighty times that of the moon. The moon has no atmosphere, and its gravity is about one-sixth that of the Earth.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with moon


see ask for the moon; once in a blue moon.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.