to smile or laugh at someone or something with an expression on your face that shows dislike and a lack of respect—usually + at
to express dislike and a lack of respect for someone or something in a very open way —usually + at
sneer
(noun)
an expression on a person's face that is like a smile but that shows dislike and a lack of respect for someone or something; also : a statement, criticism, etc., that shows dislike and a lack of respect