1. small ice crystals coating a cold surface; temperature at which things freeze; cool attitude, cold treatment, unfriendliness; failure (Slang). be covered with frost; give a frostlike surface to (glass, etc.); kill by frost; spread icing on a cake. frostfrost , n. [oe. frost, forst, as. forst, frost. fr. fre?san to freeze; akin to d. varst, g., ohg., icel., dan., & sw. frost