Contemptuous means showing that you think something is worthless. Not disagreement — dismissal.
It takes of. The word describes manner as much as opinion, so a contemptuous laugh, a contemptuous glance and a contemptuous refusal all communicate without argument. It is hotter than disdainful, which is cool and superior, and both are stronger than dismissive. The noun is contempt, and contempt of court is a specific offence with real consequences.
1adjectivecontemptuousShowing that you consider somebody or something worthless.
“He was openly contemptuous of the whole proposal.”
Latin
contemptus
English, today
contemptuous
From Latin contemptus (whence contempt) ous.
Etymology from Wiktionary, CC BY-SA