nose·dive 
/ˈnoʊzˌdaɪv/ noun
plural nose·dives /ˈnoʊzˌdaɪv/ noun [count] 1 : a sudden sharp drop made by an airplane with its front end pointing toward the ground
▪ The plane went into a nosedive. 2 : a sudden sharp drop in price, value, condition, etc.
▪ The stock market took a nosedive.
▪ The plane went into a nosedive.
▪ The stock market took a nosedive.
