Merriam-Webster Collegiate Dictionary - progressive

 I. adjective  Date: circa 1612  1.  a. of, relating to, or characterized by progress  b. making use of or interested in new ideas, findings, or opportunities  c. of, relating to, or constituting an educational theory marked by emphasis on the individual child, informality of classroom procedure, and encouragement of self-expression  2. of, relating to, or characterized by progression  3. moving forward or onward ; advancing  4.  a. increasing in extent or severity a ~ disease  b. increasing in rate as the base increases a ~ tax  5. often capitalized of or relating to political Progressives  6. of, relating to, or constituting a verb form that expresses action or state in progress at the time of speaking or a time spoken of  • ~ly adverb  • ~ness noun  II. noun  Date: 1846  1.  a. one that is ~  b. one believing in moderate political change and especially social improvement by governmental action  2. capitalized a member of any of various United States political parties: as  a. a member of a predominantly agrarian minor party that around 1912 split off from the Republicans; specifically Bull Moose  b. a follower of Robert M. La Follette in the presidential campaign of 1924  c. a follower of Henry A. Wallace in the presidential campaign of 1948