1. (primarily used by C/Unix programmers, but spreading) It is received wisdom that in most programs, less than 10% of the code eats 90% of the execution time; if one were to graph instruction visits versus code addresses, one would typically see a few huge spikes amidst a lot of low-level noise. Such spikes are called "hot spots" and are good candidates for heavy optimisation or hand-hacking. The term is especially used of tight loops and recursions in the code's central algorithm, as opposed to (say) initial set-up costs or large but infrequent I/O operations.
3. A screen region that is sensitive to mouse clicks, which trigger some action. Hypertext help screens are an example, in which a hot spot exists in the vicinity of any word for which additional material is available.
4. In a massively parallel computer with shared memory, the one location that all 10,000 processors are trying to read or write at once (perhaps because they are all doing a busy-wait on the same lock).
6. wireless hotspot.