A deposit of minute ice crystals formed when water vapor condenses at a temperature below freezing. A temperature low enough to cause freezing. The process of freezing. A cold or icy manner. To cover with frost. To damage or kill by frost. To cover (glass, for example) with a roughened or speckled decorative surface. To cover or decorate with icing: frost a cake. Slang To anger or upset: What really frosted me about the incident was the fact that you lied. To become covered with or as if with frost.