The Collaborative International Dictionary of English v.0.48:

Harmonic \Har*mon"ic\ (h[aum]r*m[o^]n"[i^]k), Harmonical
\Har*mon"ic*al\ (-[i^]*kal), a. [L. harmonicus, Gr. "armoniko`s;
   cf. F. harmonique. See Harmony.]
   1. Concordant; musical; consonant; as, harmonic sounds.
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            Harmonic twang! of leather, horn, and brass. --Pope.
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   2. (Mus.) Relating to harmony, -- as melodic relates to
      melody; harmonious; esp., relating to the accessory sounds
      or overtones which accompany the predominant and apparent
      single tone of any string or sonorous body.
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   3. (Math.) Having relations or properties bearing some
      resemblance to those of musical consonances; -- said of
      certain numbers, ratios, proportions, points, lines,
      motions, and the like.
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   Harmonic interval (Mus.), the distance between two notes of
      a chord, or two consonant notes.

   Harmonical mean (Arith. & Alg.), certain relations of
      numbers and quantities, which bear an analogy to musical
      consonances.

   Harmonic motion, the motion of the point A, of the foot of
      the perpendicular PA, when P moves uniformly in the
      circumference of a circle, and PA is drawn perpendicularly
      upon a fixed diameter of the circle. This is simple
      harmonic motion. The combinations, in any way, of two or
      more simple harmonic motions, make other kinds of harmonic
      motion. The motion of the pendulum bob of a clock is
      approximately simple harmonic motion.

   Harmonic proportion. See under Proportion.

   Harmonic series or Harmonic progression. See under
      Progression.

   Spherical harmonic analysis, a mathematical method,
      sometimes referred to as that of Laplace's Coefficients,
      which has for its object the expression of an arbitrary,
      periodic function of two independent variables, in the
      proper form for a large class of physical problems,
      involving arbitrary data, over a spherical surface, and
      the deduction of solutions for every point of space. The
      functions employed in this method are called spherical
      harmonic functions. --Thomson & Tait.

   Harmonic suture (Anat.), an articulation by simple
      apposition of comparatively smooth surfaces or edges, as
      between the two superior maxillary bones in man; -- called
      also harmonia, and harmony.

   Harmonic triad (Mus.), the chord of a note with its third
      and fifth; the common chord.
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The Collaborative International Dictionary of English v.0.48:

Progression \Pro*gres"sion\, n. [L. progressio: cf. F.
   progression.]
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   1. The act of moving forward; a proceeding in a course;
      motion onward.
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   2. Course; passage; lapse or process of time.
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            I hope, in a short progression, you will be wholly
            immerged in the delices and joys of religion.
                                                  --Evelyn.
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   3. (Math.) Regular or proportional advance in increase or
      decrease of numbers; continued proportion, arithmetical,
      geometrical, or harmonic.
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   4. (Mus.) A regular succession of tones or chords; the
      movement of the parts in harmony; the order of the
      modulations in a piece from key to key.
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   Arithmetical progression, a progression in which the terms
      increase or decrease by equal differences, as the numbers
      [lbrace2]2, 4, 6, 8, 1010, 8, 6, 4, 2[rbrace2] by the
      difference 2.
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   Geometrical progression, a progression in which the terms
      increase or decrease by equal ratios, as the numbers
      [lbrace2]2, 4, 8, 16, 32, 6464, 32, 16, 8, 4, 2[rbrace2]
      by a continual multiplication or division by 2.
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   Harmonic progression, a progression in which the terms are
      the reciprocals of quantities in arithmetical progression,
      as 1/2, 1/4, 1/6, 1/8, 1/10.
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WordNet (r) 3.0 (2006):

harmonic progression
    n 1: (mathematics) a progression of terms whose reciprocals form
         an arithmetic progression