expression, godan verb (-ru)
release the shutter; click the shutter
Photographic expression for pressing the shutter button to take a picture. The verb 切る here conveys a decisive action.
彼はカメラを構えてシャッターを切った。
He aimed the camera and pressed the shutter.
いい瞬間にシャッターを切るのは難しい。
It's hard to click the shutter at the right moment.