Getting someone fired is the act of causing someone to lose their job. This can be done through a variety of means, such as providing evidence of misconduct to their employer, spreading rumors about them, or simply making their life so difficult that they quit.
There are a number of reasons why someone might want to get someone fired. Perhaps they are jealous of the person’s success, or they feel threatened by them. In some cases, people may even get someone fired simply because they dislike them.