The opposite of being sassy is to be polite, mannerly or courteous.
Polite, mannerly and courteous means to act with good manners and respect others.
Other antonyms for sassy include, meek, timid, shy, humble, modest, self effacing as well as deferential and genteel.
Deferential and Genteel means to show polite submission or respectful compliance.
Humble, Modest, Self effacing is avoiding unnecessary attention or bold claims.
Meek, Timid and Shy is being quiet, gentle, and hesitant to speak out or challenge authority.
Sassy is an informal adjective meaning bold, spirited, confident, and sometimes playfully or mildly disrespectful.
Core Meanings of being sassy include:
Disrespectful or impudent: Talking back, teasing, or pushing boundaries against authority figures in a non-serious or cheeky way (e.g., "Don't be sassy with your parents").
Confident and energetic: Showing a lively, self-assured, and outgoing attitude (e.g., a bold strut or a playful wink).
Distinctively stylish: Describing sharp, trendy, or eye-catching fashion items (e.g., a "sassy blazer" or "sassy shoes").
Common synonyms of sassy include:
Impudent.
Fresh.
Brassy.
Bold.
Saucy.
Cheeky.