1. activism a policy of action to achieve a political or social goal
  2. activist a militant reformer
  3. actinism the property of radiation that enables it to produce photochemical effects
  4. atavism a reappearance of an earlier characteristic
  5. Activase a thrombolytic agent (trade name Activase) that causes fibrinolysis at the site of a blood clot; used in treating acute myocardial infarction
  6. active site the part of an enzyme or antibody where the chemical reaction occurs
  7. activistic advocating or engaged in activism
  8. activity any specific behavior
  9. negativism characterized by habitual skepticism and a disagreeable tendency to deny or oppose or resist suggestions or commands
  10. nativism the policy of perpetuating native cultures
  11. academism orthodoxy of a scholastic variety
  12. actinium a radioactive element of the actinide series
  13. ecotourism tourism to exotic or threatened ecosystems to observe wildlife or to help preserve nature
  14. Actitis a genus of Scolopacidae
  15. recidivism habitual relapse into crime
  16. active characterized by energetic movement
  17. egotism an exaggerated opinion of your own importance
  18. reductivism an art movement in sculpture and painting that began in the 1950s and emphasized extreme simplification of form and color
  19. activate put in motion
  20. collectivism a theory that the people should own the means of production