Wiktionary
j stroke
n. (context canoeing English) A paddling technique used by the sternman of a canoe that starts with a stroke perpendicular to the boat and ends with a hook behind the back of the boat. This forms a letter "J" when paddling on the right side of the boat. The technique is used to overcome the tendency of the boat to turn when paddling on one side and keep the boat going straight in the water.