noun
rock partially in water; rock emerging from water
Refers to a rock that is partly submerged and partly visible above the water surface, often in rivers or the sea.
川の中に浮岩がいくつか見える。
Several rocks can be seen partially emerging from the river.
noun
Specifically a lightweight, porous volcanic rock that can float on water.
浮岩は軽くて水に浮く。
Pumice stone is light and floats on water.
Compound of 浮 (uki, 'floating') + 岩 (iwa, 'rock'). The reading うきいわ is a straightforward combination of the kun'yomi readings.