Godan verb with 'u' ending, Intransitive verb
to come and go; to go back and forth
ふと通りに目をやると、行き交う人の中に、１人立ち止まり俺を見下ろす者がいた。As I glanced at the street there was somebody looking down at me in the middle of those walking past each other.
Also written 行交う【ゆきかう】、行きかう【ゆきかう】