海啸
hǎi xiào · HSK 7
tsunami
🌊 海 = sea + 啸 = roar/howl: a tsunami is the sea roaring
海 (hǎi) is the same 'sea' as in 海洋 ocean. 啸 (xiào) means to roar, howl, or whistle, as a wind or beast does. Put together, a tsunami is literally the sea letting out a roar.
海 — water radical 氵 + 每 (phonetic)
海 is a phono-semantic compound. The 氵 (water) radical signals the meaning—a vast body of water—while 每 supplies the sound. Originally referring to the sea or ocean, it later extended figuratively to mean 'vast' or 'a great quantity,' as in 人海 (a sea of people).