JIT
/ˌdʒeɪ-aɪ-ˈtiː/
n. “Compiling code at the exact moment it becomes useful.”
JIT, short for just-in-time compilation, is a runtime compilation strategy where source code or intermediate bytecode is translated into machine code while the program is running. Instead of compiling everything up front, the system waits, observes what code is actually being executed, and then optimizes those hot paths on the fly.