Literally, to turn a ship's rudder. Figuratively, to change direction (of policy, strategy, etc.) or make a decisive change in course.
嵐が来たので船長は舵を切って避難港へ向かった。
When the storm came, the captain turned the rudder and headed for a sheltering port.
会社は経営難を受けて、新しい事業に舵を切った。
Facing financial difficulties, the company changed course into a new business.
政府は環境政策で舵を切る決断をした。
The government decided to change course on environmental policy.