This is the 4668th most frequent Korean word.
건너는
"Crossing" or "crosses."
In this sentence, '건너는' is the present tense form of the verb '건너다,' meaning 'to cross,' and indicates the action of crossing happening currently.
그는 다리를 건너는 중입니다.
He is crossing the bridge.
Here, '건너는' works as a modifier and describes the road as the one that is being crossed.
건너는 길에는 자동차들이 많이 다녀요.
On the road being crossed, many cars pass through.
The word '건너는' attributes the action of crossing to the alley, emphasizing its characteristic in the context of the observation of lightning.