The Collaborative International Dictionary of English v.0.48:

Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
   1. An apparition; a specter. [Obs.]
      [1913 Webster]

   2. (Opt.)
      (a) The several colored and other rays of which light is
          composed, separated by the refraction of a prism or
          other means, and observed or studied either as spread
          out on a screen, by direct vision, by photography, or
          otherwise. See Illust. of Light, and Spectroscope.
      (b) A luminous appearance, or an image seen after the eye
          has been exposed to an intense light or a strongly
          illuminated object. When the object is colored, the
          image appears of the complementary color, as a green
          image seen after viewing a red wafer lying on white
          paper. Called also ocular spectrum.
          [1913 Webster]

   Absorption spectrum, the spectrum of light which has passed
      through a medium capable of absorbing a portion of the
      rays. It is characterized by dark spaces, bands, or lines.


   Chemical spectrum, a spectrum of rays considered solely
      with reference to their chemical effects, as in
      photography. These, in the usual photogrophic methods,
      have their maximum influence at and beyond the violet
      rays, but are not limited to this region.

   Chromatic spectrum, the visible colored rays of the solar
      spectrum, exhibiting the seven principal colors in their
      order, and covering the central and larger portion of the
      space of the whole spectrum.

   Continous spectrum, a spectrum not broken by bands or
      lines, but having the colors shaded into each other
      continously, as that from an incandescent solid or liquid,
      or a gas under high pressure.

   Diffraction spectrum, a spectrum produced by diffraction,
      as by a grating.

   Gaseous spectrum, the spectrum of an incandesoent gas or
      vapor, under moderate, or especially under very low,
      pressure. It is characterized by bright bands or lines.

   Normal spectrum, a representation of a spectrum arranged
      upon conventional plan adopted as standard, especially a
      spectrum in which the colors are spaced proportionally to
      their wave lengths, as when formed by a diffraction
      grating.

   Ocular spectrum. See Spectrum, 2
      (b), above.

   Prismatic spectrum, a spectrum produced by means of a
      prism.

   Solar spectrum, the spectrum of solar light, especially as
      thrown upon a screen in a darkened room. It is
      characterized by numerous dark lines called Fraunhofer
      lines.

   Spectrum analysis, chemical analysis effected by comparison
      of the different relative positions and qualities of the
      fixed lines of spectra produced by flames in which
      different substances are burned or evaporated, each
      substance having its own characteristic system of lines.


   Thermal spectrum, a spectrum of rays considered solely with
      reference to their heating effect, especially of those
      rays which produce no luminous phenomena.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spectrum
    n 1: an ordered array of the components of an emission or wave
    2: a broad range of related objects or values or qualities or
       ideas or activities

Moby Thesaurus II by Grady Ward, 1.0:

175 Moby Thesaurus words for "spectrum":
   AF, CPS, Dalmatian, EHF, HF, Hz, Indian file, MF, Maxwell triangle,
   Munsell scale, RF, SHF, UHF, VHF, VLF, afterimage, antigorite,
   array, articulation, audio frequency, bank, bogey, butterfly, buzz,
   candy cane, carrier frequency, carry, catena, catenation, chain,
   chain reaction, chaining, chameleon, cheetah, chromatic circle,
   chromatic spectrum, chromaticity diagram, chrysotile, color circle,
   color cycle, color index, color mixture curve, color solid,
   color spectrum, color system, color triangle, compass,
   complementary color, concatenation, confetti, connection,
   consecution, continuum, course, crazy quilt, cycle, cycles,
   demitint, descent, diapason, drone, eidolon, endless belt,
   endless round, extremely high frequency, file, filiation, firedog,
   frequency, frequency spectrum, full color, fundamental colors,
   gamut, ghost, gradation, half tint, halftone, harlequin, haunt,
   hertz, high frequency, hue cycle, hum, intermediate frequency,
   iris, jaguar, kilocycles, kilohertz, leopard, line, lineage,
   low frequency, lower frequencies, mackerel, mackerel sky, marble,
   marbled paper, medium frequency, megacycles, megahertz, metamer,
   moire, monochrome, monotone, mother-of-pearl, nacre, nexus, ocelot,
   ocular spectrum, opal, ophite, optical illusion, patchwork quilt,
   peacock, pendulum, periodicity, phantasm, plenum, powder train,
   primary, primary color, progression, pure color, queue,
   radio frequency, radius, rainbow, range, rank, reach, recurrence,
   register, reticulation, revenant, rotation, round, routine, row,
   run, scale, scope, secondary, secondary color, sequence, series,
   serpentine, serpentine marble, shade, shot silk, single file,
   solar spectrum, spark frequency, spectral color, spectrum color,
   spirit, spook, stretch, string, succession, superhigh frequency,
   swath, sweep, tertiary, tertiary color, thread, tier,
   tortoise shell, train, trick of eyesight, ultrahigh frequency,
   upper frequencies, very high frequency, very low frequency,
   windrow, zebra



The Free On-line Dictionary of Computing (30 December 2018):

ZX Spectrum
Spectrum

    Sinclair's first personal computer with a colour
   display.  The Spectrum used the Zilog Z80 processor like its
   predecessors the ZX-80 and ZX-81.  It was originally
   available in 16k and 48k versions using cassette tape and
   later grew to 128k and sprouted floppy disks.  It had a
   wider and more solid case and a marginally better "dead flesh"
   keyboard.  Unlike the earlier models, it didn't require the
   presence of a cold carton of milk to prevent it overheating.
   It was possibly the most popular home computer in the UK for
   many years.

   The TK-90X was a clone.

   (1995-11-04)