: a rapid decline or deterioration (as in strength, position, or condition) : downfall
If "dégringolade" looks French to you, you have a good eye. We lifted this noun directly from French, and even in English it is usually styled with an acute accent over the first "e," as in French. The French noun in turn comes from the verb "dégringoler" ("to tumble down"), which itself derives from the Middle French "desgringueler" (from "des-," meaning "down," and "gringueler," meaning "to tumble"). Although "dégringolade" retains the sense of a sudden tumble in English, it tends to be applied to more metaphorical situations -- a rapid fall from a higher position in society, for example. These days, "dégringolade" is fairly rare in American English. We rely far more heavily on its familiar synonym "downfall."
It's funny that they never mention the word degrade. That was the first thing that came to my mind when I saw that word.