This is the 1528th most frequent German word.
bist
"Bist" means "are" (second person singular of the verb "to be").
In this sentence, 'bist' is the conjugated form of the verb 'sein' for the second person singular in the present tense.
Du bist klug.
You are smart.
Here, 'bist' is used as part of a question structure involving the second person singular.
Bist du bereit?
Are you ready?
In this example, 'bist' establishes the subject's identity or occupation in the second person singular.