沉没 (chén mò) is a compound verb meaning 'to sink'—especially of ships, boats, or other large objects in water—and more broadly 'to submerge' or 'to go under'. The first character 沉 means 'to sink', 'to settle', or 'to become heavy'; the second character 没 means 'to submerge', 'to disappear beneath a surface', or 'to be swallowed up'. Together, they emphasize complete descent below the waterline or into obscurity. Unlike 沉 (chén) alone—which can describe gradual sinking or emotional heaviness—沉没 stresses finality and physical disappearance.

This word is commonly used in news reports, maritime contexts, historical accounts, and disaster descriptions. It’s neutral in register but carries gravity; you wouldn’t use it for small objects like a spoon falling into soup. It can also appear metaphorically—for example, describing an idea or culture ‘sinking into oblivion’—though such usage is literary and less frequent in everyday speech.