Meaning of “tumble” - Learner’s Dictionary

tumble

verb [ I ] uk us /ˈtʌmbl/
FALL

to suddenly fall:

He tumbled down the stairs.
BECOME LOWER

If the price or value of something tumbles, it suddenly becomes lower:

Share prices tumbled by 20%.
tumble noun [ C ]

(Definition of “tumble” from the Cambridge Learner’s Dictionary © Cambridge University Press)