derision
Harsh, mean mocking that makes someone feel foolish.
Derision is harsh mockery or contempt that makes someone feel small and foolish. When people treat an idea with derision, they laugh at it scornfully, as if it's too ridiculous to take seriously. When someone speaks with derision in their voice, you can hear the sneering tone that communicates “this is stupid and so are you.”
Imagine a student nervously sharing a creative idea in class, and another student responds with eye-rolling and sarcastic laughter. That mocking response is derision. It's different from friendly teasing or honest criticism. Derision aims to humiliate and dismiss rather than help or engage.
A derisive comment cuts deeper than simple disagreement because it attacks not just the idea but the person behind it. When someone meets your suggestion with derisive laughter, they're signaling that they think your idea doesn't even deserve consideration.
Many breakthrough ideas have initially faced derision. People mocked the Wright brothers' attempts to build a flying machine. Scientists treated the idea of continental drift with derision for decades before evidence proved it true.