Definition - What does Deadlock mean?
In general computing, a deadlock is a situation where two different programs or processes depend on one another for completion, either because both are using the same resources or because of erroneous cues or other problems.
Techopedia explains Deadlock
Modern operating systems use various threads and multitasking for programs and processes. There are certain situations where the operating system may fail to manage a deadlock, causing processes to hang or freeze. Dealing with this is a major part of software engineering. For example, there can be a situation where two threads start and request resources from each other, and neither can go forward. This will require a significant observation of processes and changes that will work around these hangups.