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.
He paddled the water with an oar.
He paddled the small boat with an oar.
I forgot the oars for the boat.
The boatman gripped the oar firmly.
櫓 is a larger sculling oar mounted on the stern and worked with a twisting wrist motion, whereas 櫂 is a handheld paddle used for direct strokes.
Standard kanji spelling for 'paddle/oar'.
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.