kipuka is Hawaiian for "island" or "park", but in geomorphology, it refers to a type of (volcanic) landform, a patch of land that has been surrounded by a lava flow. After the lava has cooled, the original vegetation may still be there, resulting in an island of greenery in an otherwise desolate landscape.
A kipuka can result from streams of lava branching around a slightly higher spot and rejoining downstream, but the terrain doesn't necessarily have to be higher. It could be that converging streams of lava died out and cooled before covering that spot.
There are more specialized terms for more specialized types of kipukas, such as steptoe for a remnant hill from an ancient eroded landscape poking through a lava field.