to turn (one's face/body) to the side; to look away or avert one's gaze.
話しかけられると彼はすぐに横を向いた。
When spoken to, he immediately turned away.
授業中に友達が横を向いて私にウインクした。
During class a friend turned to the side and winked at me.
彼女は写真を撮られるのが嫌で、カメラの方に横を向いた。
She didn't like being photographed, so she turned to the side of the camera.