Cassis is primarily known for being a blackcurrant liqueur, but it's also a commonly used term to refer to the blackcurrant fruit itself. If you need to describe the fruit, some possible synonyms could be "currant," "blackberry," or "berry." However, if you're referring specifically to the liqueur, some possible synonyms might include "blackcurrant brandy," "creme de cassis," or "blackcurrant schnapps." Other related terms might include "fruit liqueur," "cordial," or "alcoholic beverage." Whatever word you choose, make sure it accurately conveys the meaning or concept you're trying to express.