Fundamentalistic is a term used to describe someone who strictly adheres to a set of foundational principles or beliefs. However, there are several synonyms to this word that could be used to convey a similar meaning. Some of these words include puritanical, dogmatic, rigid, orthodox, and doctrinal. While each of these words has a slightly different connotation, they all share the common theme of being uncompromising in their beliefs. These synonyms provide alternative ways to describe individuals who are deeply committed to a particular ideology or philosophy. It is important to keep in mind that the use of synonyms should be done with care, as they can carry different shades of meaning and emphasis.