expression
as one turns around; the moment one turns around
Describes an action that happens at the same time as, or immediately after, turning around. Often used in narrative to describe a sudden action or event occurring while turning.
See also: ざま
振り向きざまに彼は微笑んだ。
He smiled as he turned around.
振り向きざま、誰かに肩を叩かれた。
Just as I turned around, someone tapped me on the shoulder.
Compound of 振り向き (continuative form of 振り向く 'to turn around') + ざま (suffix indicating the moment or manner of an action).