"Rebis" is a term used in alchemy to describe the stage in which the substance being worked on undergoes a process of transformation and purification. Synonyms for "rebis" include "philosopher's stone," "the great work," "prima materia," and "the divine marriage." These words all refer to the same concept of transformation and purification in alchemy, and are often used interchangeably. Each of these synonyms represents a different aspect of this process, with "the great work" emphasizing the spiritual nature of the transformation, while "prima materia" highlights the importance of the original raw material being worked upon. Regardless of the term used, the goal of the alchemical process is to achieve the highest level of purity and perfection possible.