The Collaborative International Dictionary of English v.0.48:

Sun \Sun\, n. [OE. sunne, sonne, AS. sunne; akin to OFries.
   sunne, D. zon, OS. & OHG. sunna, G. sonne, Icel. sunna, Goth.
   sunna; perh. fr. same root as L. sol. [root]297. Cf. Solar,
   South.]
   1. The luminous orb, the light of which constitutes day, and
      its absence night; the central body round which the earth
      and planets revolve, by which they are held in their
      orbits, and from which they receive light and heat. Its
      mean distance from the earth is about 92,500,000 miles,
      and its diameter about 860,000.
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   Note: Its mean apparent diameter as seen from the earth is
         32' 4[sec], and it revolves on its own axis once in
         251/3 days. Its mean density is about one fourth of
         that of the earth, or 1.41, that of water being unity.
         Its luminous surface is called the photosphere, above
         which is an envelope consisting partly of hydrogen,
         called the chromosphere, which can be seen only through
         the spectroscope, or at the time of a total solar
         eclipse. Above the chromosphere, and sometimes
         extending out millions of miles, are luminous rays or
         streams of light which are visible only at the time of
         a total eclipse, forming the solar corona.
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   2. Any heavenly body which forms the center of a system of
      orbs.
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   3. The direct light or warmth of the sun; sunshine.
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            Lambs that did frisk in the sun.      --Shak.
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   4. That which resembles the sun, as in splendor or
      importance; any source of light, warmth, or animation.
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            For the Lord God is a sun and shield. --Ps. lxxiv.
                                                  11.
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            I will never consent to put out the sun of
            sovereignity to posterity.            --Eikon
                                                  Basilike.
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   Sun and planet wheels (Mach.), an ingenious contrivance for
      converting reciprocating motion, as that of the working
      beam of a steam engine, into rotatory motion. It consists
      of a toothed wheel (called the sun wheel), firmly secured
      to the shaft it is desired to drive, and another wheel
      (called the planet wheel) secured to the end of a
      connecting rod. By the motion of the connecting rod, the
      planet wheel is made to circulate round the central wheel
      on the shaft, communicating to this latter a velocity of
      revolution the double of its own. --G. Francis.

   Sun angel (Zool.), a South American humming bird of the
      genus Heliangelos, noted for its beautiful colors and
      the brilliant luster of the feathers of its throat.

   Sun animalcute. (Zool.) See Heliozoa.

   Sun bath (Med.), exposure of a patient to the sun's rays;
      insolation.

   Sun bear (Zool.), a species of bear (Helarctos Malayanus)
      native of Southern Asia and Borneo. It has a small head
      and short neck, and fine short glossy fur, mostly black,
      but brownish on the nose. It is easily tamed. Called also
      bruang, and Malayan bear.

   Sun beetle (Zool.), any small lustrous beetle of the genus
      Amara.

   Sun bittern (Zool.), a singular South American bird
      (Eurypyga helias), in some respects related both to the
      rails and herons. It is beautifully variegated with white,
      brown, and black. Called also sunbird, and tiger
      bittern.

   Sun fever (Med.), the condition of fever produced by sun
      stroke.

   Sun gem (Zool.), a Brazilian humming bird (Heliactin
      cornutus). Its head is ornamented by two tufts of bright
      colored feathers, fiery crimson at the base and greenish
      yellow at the tip. Called also Horned hummer.

   Sun grebe (Zool.), the finfoot.

   Sun picture, a picture taken by the agency of the sun's
      rays; a photograph.

   Sun spots (Astron.), dark spots that appear on the sun's
      disk, consisting commonly of a black central portion with
      a surrounding border of lighter shade, and usually seen
      only by the telescope, but sometimes by the naked eye.
      They are very changeable in their figure and dimensions,
      and vary in size from mere apparent points to spaces of
      50,000 miles in diameter. The term sun spots is often used
      to include bright spaces (called faculae) as well as dark
      spaces (called maculae). Called also solar spots. See
      Illustration in Appendix.

   Sun star (Zool.), any one of several species of starfishes
      belonging to Solaster, Crossaster, and allied genera,
      having numerous rays.

   Sun trout (Zool.), the squeteague.

   Sun wheel. (Mach.) See Sun and planet wheels, above.

   Under the sun, in the world; on earth. "There is no new
      thing under the sun." --Eccl. i. 9.
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   Note: Sun is often used in the formation of compound
         adjectives of obvious meaning; as, sun-bright,
         sun-dried, sun-gilt, sunlike, sun-lit, sun-scorched,
         and the like.
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