When someone is supercilious, they act like they are better than other people.
Being supercilious is not nice because it makes other people feel bad.
Examples:
She has a supercilious attitude towards her classmates.
His supercilious behavior makes others feel small.
The supercilious girl never wants to play with others.
He looks supercilious when he talks about his grades.
The queen's supercilious manner made everyone feel unimportant.
The cat looked supercilious as it walked by.