When someone is snide, they are unkind or mocking in a sly or mean way.
Snideness is not nice and can hurt people's feelings.
Examples:
Her snideness made me feel sad.
I don't like his snideness.
The snideness in her voice was clear.
His snideness was like a little bug, annoying and hard to get rid of.
The snideness in the room was so big, it felt like a dark cloud.
The snideness in his words stuck to me like sticky candy.