only when

n an antiarrhythmic drug (trade name Cordarone) that has potentially fatal side effects and is used to control serious heart rhythm problems only when safer agents have been ineffective

especially an image distorted in such a way that it becomes visible only when viewed in a special manner

a branch of a river made by water flowing from the main stream only when the water level is high

tropical American evergreen tree bearing kidney-shaped nuts that are edible only when roasted n

kidney-shaped nut edible only when roasted