"FUNDAMENTALISM should be understood primarily as an attempt to protect the central doctrines or elements (fundamentals) of the Christian faith from the eroding effects of modern thought." (Such as the Virgin Birth and the bodily Resurrection of Christ).
Fundamentalism resists the encroachment of scientism into areas of faith. (For example, the theory of evolution). Fundamentalism tends to be separatist. It tends to withdraw from the world in order to avoid contamination of biblical purity.