Signal Catch - when a signal is received by a thread by the RTOS scheduler on behalf of the thread - the catch modifies the catching threadís state such that the PC, registers, and stack are saved and when the thread is dispatched next, the scheduler dispatches the threads registered signal handler rather than where it was last preempted.
Signal Throw - when a thread wants to asynchronously interrupt the normal flow of execution of another thread, it can call an RTOS mechanism to throw a signal to the other thread instructing the RTOS to dispatch the other threadís signal handler rather than itís last context.
Slack Time - on a real-time system, when no real-time services are requesting CPU time (I.e. waiting on the ready queue or actively running), this unused CPU time is called slack time and often can be used for non real-time best effort processing. Slack time is often created by service releases where the actual execution time taken is much shorter than WCET due to execution jitter.
SoC - System On-a-Chip, an ASIC which includes one or more CPU cores, a bus, and I/O interfaces such that it essentially places devices previously on a board in earlier products on a single ASIC.