"Lock-free" refers to a type of concurrent programming design that allows multiple threads to access shared data without using traditional locking mechanisms. This approach helps to avoid issues like deadlocks and reduces the time threads spend waiting for access, which can improve performance in multi-threaded applications. In a lock-free system, operations on shared data are designed to ensure that at least one thread can make progress at any given time. This is often achieved through atomic operations and techniques like compare-and-swap. Lock-free programming is commonly used in high-performance computing and real-time systems where responsiveness is critical.