The Collaborative International Dictionary of English v.0.48:

Progressive \Pro*gress"ive\, a. [Cf. F. progressif.]
   [1913 Webster]
   1. Moving forward; proceeding onward; advancing; evincing
      progress; increasing; as, progressive motion or course; --
      opposed to retrograde.
      [1913 Webster]

   2. Improving; as, art is in a progressive state.
      [1913 Webster]

   3. (U. S. History) Of or pertaining to the Progressive party.
      [Webster 1913 Suppl.]

   4. Favoring improvement, change, progress, or reform,
      especially in a political context; -- used of people.
      Contrasted with conservative.
      [PJC]

   Note: The term progressive is sometimes used to describe the
         views of a politician, where liberal might have been
         used at one time, in communities where the term liberal
         has come to connote extreme views.
         [PJC]

   5. Disposed toward adopting new methods in government or
      education, holding tolerant and liberal ideas, and
      generally favoring improvement in civic life; -- of towns
      and communities.
      [PJC]

   Progressive euchre or Progressive whist, a way of playing
      at card parties, by which after every game, the losers at
      the first table go to the last table, and the winners at
      all the tables, except the first, move up to the next
      table.

   Progressive muscular atrophy (Med.), a nervous disorder
      characterized by continuous atrophy of the muscles.
      [1913 Webster] -- Pro*gress"ive*ly, adv. --
      Pro*gress"ive*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

progressive
    adj 1: favoring or promoting progress; "progressive schools"
           [ant: regressive]
    2: favoring or promoting reform (often by government action)
       [syn: progressive, reformist, reform-minded]
    3: (of taxes) adjusted so that the rate increases as the amount
       of income increases [ant: regressive]
    4: gradually advancing in extent
    5: (of a card game or a dance) involving a series of sections
       for which the participants successively change place or
       relative position; "progressive euchre"; "progressive
       tournaments"
    6: advancing in severity; "progressive paralysis"
    n 1: a tense of verbs used in describing action that is on-going
         [syn: progressive, progressive tense, imperfect,
         imperfect tense, continuous tense]
    2: a person who favors a political philosophy of progress and
       reform and the protection of civil liberties [syn: liberal,
       liberalist, progressive] [ant: conservative,
       conservativist]

Moby Thesaurus II by Grady Ward, 1.0:

119 Moby Thesaurus words for "progressive":
   Fabian, a la mode, advanced, advancing, ameliorative, ascending,
   avant-garde, axial, back, back-flowing, backward, bettering,
   catenary, consecutive, contemporary, continuing, continuous,
   descending, developing, down-trending, downward, drifting, dynamic,
   extremist, far out, fashionable, flowing, fluent, flying, forward,
   forward-looking, go-ahead, going, gradual, growing, gyrational,
   gyratory, improving, in, increasing, left, left of center,
   left-wing, left-winger, leftist, liberal, liberalist, liberalistic,
   lineal, linear, looking up, meliorative, meliorist, mending, mod,
   modern, modernistic, modernized, modish, mounting, moving,
   newfashioned, now, on the left, on the lift, on the mend, oncoming,
   ongoing, onward, ordinal, passing, plunging, present-day,
   present-time, proceeding, progressing, progressionist, progressist,
   progressivist, progressivistic, radical, reflowing, refluent,
   reformer, reformist, regressive, retrogressive, revisionist,
   revolutionary, rising, rotary, rotational, rotatory, running,
   rushing, sequent, sequential, serial, seriate, sideward, sinking,
   soaring, step by step, streaming, streamlined, successional,
   successive, twentieth-century, ultra-ultra, ultramodern,
   up-to-date, up-to-datish, up-to-the-minute, up-trending, upward,
   utopian, utopist, way out, welfare stater