Post History
In this context, I would take it to mean someone who cannot be reasoned with. When dealing with a mountain or a rainstorm, you can't reason with them or reach a deal or a compromise with them. When...
Answer
#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/27880 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/27880 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
In this context, I would take it to mean someone who cannot be reasoned with. When dealing with a mountain or a rainstorm, you can't reason with them or reach a deal or a compromise with them. When you are dealing with a normal human being, on the other hand, you can reason with them or make a deal with them. To describe a person as a force of nature, is to say that you can't bargain with them or reach a deal with them. They are as implacable as a mountain or a rain storm. The term is used in much looser sense as well, to describe someone of great energy or abundant personality, but I think it is the sense described above that most likely fits the intent in the examples you cite.