Whiny describes someone who complains in an annoying, high-pitched voice, often about small problems that don't deserve that much fuss. A whiny child might drag out their words in a nasal tone: “But I don't waaaaant to clean my room!” A whiny teammate might constantly complain during practice: “This is too hard. Why do we have to run so much? My legs hurt.”

When applied to people, it suggests childish complaining that grates on everyone's nerves. Someone being whiny expresses their unhappiness in a way that makes others want to walk away, using that characteristic high-pitched, drawn-out tone.

There's a big difference between raising a legitimate concern and being whiny. If the cafeteria serves spoiled food, speaking up is responsible. But complaining endlessly because they're serving green beans instead of corn? That's whiny.