What does 'compile time' mean in C programming?

Compile Time: In longer form, you might say, "at the time of compiling", or, "when the program is compiled".
When you compile a program, the compiler applies various processes to your source code in order to generate the executable files. These are actions that happen "at compile time".
Other actions happen when you actually run the finished program. These actions are said to occur, at, or in, "run time".