The Collaborative International Dictionary of English v.0.48:

Progression \Pro*gres"sion\, n. [L. progressio: cf. F.
   progression.]
   [1913 Webster]
   1. The act of moving forward; a proceeding in a course;
      motion onward.
      [1913 Webster]

   2. Course; passage; lapse or process of time.
      [1913 Webster]

            I hope, in a short progression, you will be wholly
            immerged in the delices and joys of religion.
                                                  --Evelyn.
      [1913 Webster]

   3. (Math.) Regular or proportional advance in increase or
      decrease of numbers; continued proportion, arithmetical,
      geometrical, or harmonic.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

progression
    n 1: a series with a definite pattern of advance [syn:
         progression, patterned advance]
    2: a movement forward; "he listened for the progress of the
       troops" [syn: progress, progression, advance]
    3: the act of moving forward (as toward a goal) [syn:
       progress, progression, procession, advance,
       advancement, forward motion, onward motion] [ant:
       retreat]

Moby Thesaurus II by Grady Ward, 1.0:

157 Moby Thesaurus words for "progression":
   Great Leap Forward, Indian file, accomplishment, advance,
   advancement, alternation, amelioration, amendment, amplification,
   array, articulation, ascension, ascent, bank, bettering,
   betterment, blossoming, boost, broadening, buzz, catena,
   catenation, chain, chain reaction, chaining, coming after,
   concatenation, connection, consecution, consecutiveness,
   continualness, continuance, continuation, continuity, continuum,
   course, cycle, descent, development, developmental change, drone,
   elaboration, elevation, endless belt, endless round, endurance,
   enhancement, enlargement, enrichment, eugenics, euthenics,
   evolution, evolutionary change, evolvement, evolving, expansion,
   explication, extending, extension, file, filiation, flow,
   flowering, following, furtherance, gamut, geometrical progression,
   gradation, gradual change, growth, headway, hum, improvement,
   intensification, lengthening, lift, line, lineage,
   logical sequence, maintenance, maturation, melioration, mend,
   mending, monotone, natural development, natural growth, nexus,
   nonviolent change, order, order of succession, pendulum,
   periodicity, perpetuation, perseverance, persistence, pickup,
   plenum, posteriority, postposition, powder train, preferment,
   procession, progress, prolongation, promotion, protraction,
   pursuance, queue, range, rank, recovery, recurrence, repetition,
   restoration, reticulation, revival, ripening, rise, rotation,
   round, routine, row, run, scale, sequel, sequence, series,
   single file, spectrum, spread, spreading, staying power,
   straight course, string, subjunction, succession, successiveness,
   suffixation, sustained action, sustenance, swath, thread, tier,
   train, unfolding, uninterrupted course, unremittingness, upbeat,
   upgrowth, uplift, upping, upswing, uptrend, upward mobility, way,
   windrow