The phrase "never in wildest dreams" is an idiom used to express disbelief or surprise about something unexpected happening. There are several synonyms for this phrase including "unimaginable," "unthinkable," "inconceivable," "impossible," "unfathomable," and "beyond belief." These words can be used interchangeably with "never in wildest dreams" to express a similar idea. For example, one could say, "It was inconceivable that she would win the election," or "I never imagined in my wildest dreams that I would meet a celebrity." These synonyms for "never in wildest dreams" can add variety and depth to one's writing or conversation.