Here is my compilation of Wikipedia, thefreedictionary.com and other sources.
Unwavering attachment to a set of irreducible beliefs. Strict adherence to certain scriptures, dogmas, or ideologies.
Related to the base, the principal mission statement of a corporation.
Fundamentalism is a tendency among certain groups (e.g. Christianism, Islamism, Capitalism).
Fundamentalism is characterized by an emphasis on purity and the desire to return to “the fundamental principles” or the established (“proven”, “accepted”) interpretation of the group’s Holy Scripture. A good fundamentalist refuses diversity of opinion regarding these principles and their interpretation within the group. A good fundamentalist finds it important to differentiate between members and non-members of the group, which can lead to intolerance of other views.