The word "jadis" is an old French word that means "formerly" or "once." It is a term that typically denotes a bygone era or a time that has since passed. There are several synonyms for the word "jadis," including "once upon a time," "a long time ago," "previously," "in the past," and "once." Other synonyms could include "formerly," "earlier," "at one time," and "in days gone by." All of these words seek to convey the idea of a time that has passed, whether that be yesterday or centuries ago. Ultimately, the word "jadis" and its synonyms are used to evoke nostalgia and a sense of timelessness.