This is the 372nd most frequent Vietnamese word.
bị
"bị": A marker indicating a passive voice or an adverse/unwanted action.
In this sentence, 'bị' introduces an adverse condition or situation affecting the subject (being sick).
Tôi bị ốm.
I am sick.
Here, 'bị' is used to indicate an action received passively and usually unpleasantly by the subject (being scolded).
Anh ấy bị mắng bởi giáo viên.
He was scolded by the teacher.
In this context, 'bị' shows an occurrence of damage to the object (the tree) due to an external factor (the wind).