What is Curdle ?
Curdle is (verb) 1. to become or make something become solid and sour If you add lemon juice to milk it will curdle it. Milk will curdle in hot weather. 2. to make your blood curdle to make you very frightened a story frightening enough to make their blood curdle One’s blood curdles at the mere thought of it. bloodcurdling
source: Easier English, Student Dictionary Upper Intermediate Level