When someone is described as being "to the core," it implies that they are completely and consistently a certain way. Synonyms for this phrase include "deeply ingrained," "fundamental," or "innate." A person who is completely honest might be described as "honest to the core," while someone with a strong sense of loyalty may be "loyal to the core." Other ways to express this sentiment include "deeply rooted," "integral," or "inherent." To be "to the core" is to possess an unchanging and unwavering quality, making it an impactful way to describe someone with unwavering values or beliefs.