Definition:
A "phylactery" is a noun that refers to one of two small leather boxes that contain texts from the Hebrew scriptures. These boxes are called "tefillin" in Hebrew. They are traditionally worn by Jewish men on their forehead and left arm during morning prayers.
In more advanced contexts, you might discuss the symbolism of phylacteries, such as how they represent the binding of the heart and mind to God's commandments.
While "phylactery" primarily refers to the Jewish religious item, in ancient contexts, it could also refer to a charm or amulet believed to protect against evil or misfortune. However, this usage is much less common in modern English.
In summary, "phylactery" is a specialized term used in Judaism to describe a religious object that plays a significant role in daily prayers.