Ism/ˈɪzəm/ Definition 1 of 4Pro Tip 1/3Ideological Movements Used to describe a movement or ideology someone identifies with or follows. She advocates for environmentalism. Pro Tip 2/3Endorse or Criticize May indicate support for or criticism of a theory, like 'Darwinism' could imply acceptance or scorn. Darwinism is often misunderstood. Pro Tip 3/3Common Ideals Suggests a shared ideology within a group, not just individual beliefs. Collectivism is valued in many societies.