TCC isn't a JIT-compiler, the script-option compiles all and then runs it on the fly. This allows C-files to be executable by themselves with a shebang-line.

It's also usable as a dynamic load library. It's still not a JIT, but a program can use it to run code directly without having to fork/exec/spawn anything.

I guess in some sense that could also be described as "just in time," i.e. just before you need to run it.

I've heard the phrase "just-before-time" (or JBT) for this, i.e. compiling on the target machine.