General terms:
* Falling rock: This is the most straightforward and common description.
* Rockfall: This term refers to the event of the rock falling, rather than the rock itself.
* Debris: This is a more general term that could refer to any material falling from the cliff, including rocks.
More descriptive terms:
* Boulder: This term is used for a large rock, highlighting its size.
* Loose rock: This emphasizes that the rock was not firmly attached to the cliff.
* Unstable rock: This highlights the danger posed by the falling rock.
Ultimately, the best word depends on the context and what you want to emphasize.
