To sass someone means to talk back to them in a rude, disrespectful, or cheeky way, especially to someone in authority like a parent or teacher. When a student sasses their teacher by rolling their eyes and saying “whatever” instead of “yes, ma'am,” they're being deliberately disrespectful.

Sass sits somewhere between playful teasing and outright rudeness. The exact line depends on tone, relationship, and context. Friends might sass each other playfully during a game: “Oh, you think you're going to win? That's adorable!” But the same words to a coach or parent would sound disrespectful.

As a noun, sass means that bold, back-talking attitude itself: “Don't give me any sass, young lady!” Someone with a lot of sass speaks their mind boldly, sometimes too boldly. In some contexts, being sassy can mean confident and spirited rather than rude. A sassy character in a book might be funny and bold without being mean.

The key difference: playful sass makes people laugh; disrespectful sass makes people upset. Knowing which is which requires paying attention to how your words affect others.