This is the 16524th most frequent Russian word.
сбитым
"Сбитым" means "knocked down" or "shot down" in English.
In this sentence, "сбитым" is used as an adjective describing the state of the leaves as being knocked off from the trees, showing an effect caused by external force.
После сильного ветра листва с деревьев была сбитым.
After strong winds, the leaves were knocked off the trees.
Here, the word "сбит" (root related to "сбитым") acts in past tense form and denotes an action performed by the subject of knocking off the object in a specific manner.
Его прицельный выстрел сбил шляпу с ветки.
His accurate shot knocked the hat off the branch.
The word "сбитым" in this context metaphorically describes the mood of the subject as being defeated or knocked off balance emotionally.