The Collaborative International Dictionary of English v.0.48:

Sphere \Sphere\, n. [OE. spere, OF. espere, F. sph[`e]re, L.
   sphaera,. Gr. ??? a sphere, a ball.]
   1. (Geom.) A body or space contained under a single surface,
      which in every part is equally distant from a point within
      called its center.
      [1913 Webster]

   2. Hence, any globe or globular body, especially a celestial
      one, as the sun, a planet, or the earth.
      [1913 Webster]

            Of celestial bodies, first the sun,
            A mighty sphere, he framed.           --Milton.
      [1913 Webster]

   3. (Astron.)
      (a) The apparent surface of the heavens, which is assumed
          to be spherical and everywhere equally distant, in
          which the heavenly bodies appear to have their places,
          and on which the various astronomical circles, as of
          right ascension and declination, the equator,
          ecliptic, etc., are conceived to be drawn; an ideal
          geometrical sphere, with the astronomical and
          geographical circles in their proper positions on it.
      (b) In ancient astronomy, one of the concentric and
          eccentric revolving spherical transparent shells in
          which the stars, sun, planets, and moon were supposed
          to be set, and by which they were carried, in such a
          manner as to produce their apparent motions.
          [1913 Webster]

   4. (Logic) The extension of a general conception, or the
      totality of the individuals or species to which it may be
      applied.
      [1913 Webster]

   5. Circuit or range of action, knowledge, or influence;
      compass; province; employment; place of existence.
      [1913 Webster]

            To be called into a huge sphere, and not to be seen
            to move in 't.                        --Shak.
      [1913 Webster]

            Taking her out of the ordinary relations with
            humanity, and inclosing her in a sphere by herself.
                                                  --Hawthorne.
      [1913 Webster]

            Each in his hidden sphere of joy or woe
            Our hermit spirits dwell.             --Keble.
      [1913 Webster]

   6. Rank; order of society; social positions.
      [1913 Webster]

   7. An orbit, as of a star; a socket. [R.] --Shak.
      [1913 Webster]

   Armillary sphere, Crystalline sphere, Oblique sphere,.
      See under Armillary, Crystalline,.

   Doctrine of the sphere, applications of the principles of
      spherical trigonometry to the properties and relations of
      the circles of the sphere, and the problems connected with
      them, in astronomy and geography, as to the latitudes and
      longitudes, distance and bearing, of places on the earth,
      and the right ascension and declination, altitude and
      azimuth, rising and setting, etc., of the heavenly bodies;
      spherical geometry.

   Music of the spheres. See under Music.
      [1913 Webster]

   Syn: Globe; orb; circle. See Globe.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sphere \Sphere\, v. t. [imp. & p. p. Sphered; p. pr. & vb. n.
   Sphering.]
   1. To place in a sphere, or among the spheres; to insphere.
      [1913 Webster]

            The glorious planet Sol
            In noble eminence enthroned and sphered
            Amidst the other.                     --Shak.
      [1913 Webster]

   2. To form into roundness; to make spherical, or spheral; to
      perfect. --Tennyson.
      [1913 Webster] Spherical

WordNet (r) 3.0 (2006):

sphere
    n 1: a particular environment or walk of life; "his social
         sphere is limited"; "it was a closed area of employment";
         "he's out of my orbit" [syn: sphere, domain, area,
         orbit, field, arena]
    2: any spherically shaped artifact
    3: the geographical area in which one nation is very influential
       [syn: sphere, sphere of influence]
    4: a particular aspect of life or activity; "he was helpless in
       an important sector of his life" [syn: sector, sphere]
    5: a solid figure bounded by a spherical surface (including the
       space it encloses)
    6: a three-dimensional closed surface such that every point on
       the surface is equidistant from the center
    7: the apparent surface of the imaginary sphere on which
       celestial bodies appear to be projected [syn: celestial
       sphere, sphere, empyrean, firmament, heavens, vault
       of heaven, welkin]

Moby Thesaurus II by Grady Ward, 1.0:

208 Moby Thesaurus words for "sphere":
   Aldebaran, Canicula, Dog Star, Hesper, Hesperus, Lucifer,
   North Star, Phosphor, Phosphorus, Polaris, Sirius, Venus, Vesper,
   academic discipline, academic specialty, acreage, agora, ambit,
   amphitheater, applied science, area, arena, art, athletic field,
   auditorium, background, bag, bailiwick, ball, balloon, bear garden,
   beat, bladder, blob, boll, bolus, border, borderland, bowl,
   boxing ring, breadth, bubble, bulb, bulbil, bulblet, bull ring,
   campus, canvas, caste, celestial body, champaign, circle, circuit,
   circus, class, cockpit, coliseum, colosseum, comet, concern,
   condition, continuum, course, daystar, demesne, department,
   department of knowledge, dimension, discipline, domain, dominion,
   drop, droplet, echelon, ellipsoid, emptiness, empty space,
   ensphere, evening star, expanse, expansion, extension, extent,
   field, field of inquiry, field of study, fixed stars, floor,
   footing, forte, forum, galactic space, geoid, globe, globelet,
   globoid, globule, glomerulus, gob, gobbet, ground, gym, gymnasium,
   hall, heavenly body, hemisphere, hierarchy, hippodrome,
   infinite space, interstellar space, judicial circuit, jurisdiction,
   knob, knot, level, lists, living sapphires, locale, lodestar,
   march, marketplace, mat, measure, milieu, morning star,
   natural science, nothingness, oblate spheroid, ology, open forum,
   orb, orbit, orblet, order, outer space, palaestra, pale,
   parade ground, pellet, pit, place, platform, polar star, polestar,
   position, power structure, precedence, precinct, prize ring,
   prolate spheroid, proportion, province, public square,
   pure science, purlieu, range, rank, rate, rating, realm, ring,
   rondure, round, scene, scene of action, scenery, science, setting,
   site, social science, society, space, spatial extension, specialty,
   spheroid, spherule, spread, squared circle, stadium, stage,
   stage set, stage setting, standing, starry host, stars, station,
   status, stratum, study, subdiscipline, subject,
   superficial extension, surface, technicology, technics, technology,
   terrain, territory, theater, thing, tilting ground, tiltyard,
   tract, void, volume, walk, walk of life, wrestling ring