Tsunami, Tidal Wave
noun
A harbor wave is a wave big enough, it could easily submerge an entire harbor. What could you call such a wave? Perhaps a tsunami, or a tidal wave.
つなみ
The reading is the 津 and 波 kun'yomi readings, combined together.
たくさんの人達が津波に流されてしまいました。
Many people were swept away by the tsunami.