Still less is a phrase that is commonly used to indicate that something is even more unlikely or impractical than the previous statement. This phrase is often replaced by other synonyms in order to convey the same meaning but with different words. To say "still less," you could also use phrases like "even less likely," "even more improbable," and "far from being possible." Other synonyms for "still less" include "much less," "even less so," and "all the more unlikely." By using different synonyms for "still less," you can convey the same meaning with a different tone or emphasis, making your writing or speaking more effective.