水下核爆炸 shuǐxiàhébàozhà underwater nuclear explosion Origin Definitions Defs Strokes Stroke Words Sentences Sents 水下 shuǐxià locativenoun underwater under the water; submerged; submarine核爆炸 hébàozhà noun nuclear explosion A sudden and massive release of energy from a high-speed nuclear reaction; may result from fission, fusion, or both.