Use 'contemptuous' to describe someone's attitude when it's filled with strong dislike or disrespect. Her contemptuous tone made it clear she thought the idea was foolish.
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Facial Expressions
'Contemptuous' often relates to facial expressions signaling disdain, like rolling one's eyes. His contemptuous smirk gave away his true feelings about the performance.
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Social Interaction
Using 'contemptuous' can imply a social hierarchy where the speaker feels superior. She gave a contemptuous laugh when he suggested she couldn't afford the car.