slumping

1. To collapse heavily or helplessly.

   Exhausted, he slumped down onto the sofa.

2. To decline or fall off in activity or performance.

   Real estate prices slumped during the recession.

3. To slouch or droop.
4. To lump; to throw together messily.
5. To fall or sink suddenly through or in, when walking on a surface, as on thawing snow or ice, a bog, etc.
6. (slang) To cause to collapse; to hit hard; to render unsconscious; to kill.

noun

The result of a slumping movement, like that of a mountain

adjective

Something that makes a slumping voice