›mainly UKIf something that you can see through mists over/up, it becomes covered with a thin layer of liquid so that it is more difficult to see through: Open the window when you have a shower to stop the mirror misting over.The steam from the kettle misted up her glasses.→ See alsosteam (sth) upClouds, dew, fog and steam›If your eyes mist over/up, they fill with tears.Weeping and crying