Firefighting, in computing, refers to the emergency allocation of resources that are necessary to handle an unexpected problem. The term implies that the effort goes into chasing bugs rather than integrating new features.
This term can be spelt as either fire-fighting, fire fighting, or firefighting.
Techopedia explains Fire Fighting
For example, in software development, firefighting may involve the assigning of additional programmers to fix coding bugs that are identified in close proximity to a product's release date. In the context of security, firefighting may involve the allocation of resources to take care of an information system breach or a computer virus outbreak. In the individual user level, firefighting may involve the handling of software or hardware issues that might have been avoided through standard computer maintenance techniques.
Many organizations are well prepared to handle a fire-fighting situation; however, a frequently repeating emergency situation reflects poor planning, or a lack of efficiency, and will result in the wastage of resources that are actually required somewhere else. To maintain firefighting to a minimal level, in-depth disaster recovery planning (DRP) is required, which anticipates and hopefully prevents such emergencies.