noun
Refers to a paddle or oar used for rowing or paddling a boat. 櫂 is the standard term, distinct from オール (oar) which is often used for Western-style rowing.
彼は櫂で水をかいた。
He paddled the water with an oar.
ボートに櫂を忘れてきた。
I forgot the oars for the boat.
The kanji 櫂 is a phono-semantic compound with 木 (tree/wood) and 翟 (a phonetic component). The reading かい is a native Japanese word (kun'yomi) of uncertain origin.