When it comes to describing someone as secretive or cautious, the word "cagiest" perfectly encapsulates their nature. However, there are various synonyms that can be used to convey a similar meaning. One alternative is "guarded", which implies a person's reserved and watchful demeanor. Another synonym is "reserved", suggesting a person's inclination to keep their thoughts and feelings to themselves. "Sly" can also be used to describe someone who is cunning or crafty in their actions. Lastly, "wary" can be utilized to portray someone who is cautious and alert, always on their guard. All these synonyms adequately capture the essence of a cagiest individual, each providing a slightly different shade of meaning.