The Free On-line Dictionary of Computing (30 December 2018):
The period of time during which a program's
source code is being translated into machine code, as
opposed to run time when the program is being executed. As
well as the work done by the compiler, this may include
macro preprocessing as done by cpp for example. The final
stage of program construction, performed by the linker,
would generally also be classed as compile time but might be
distinguished as link time.
For example, static data in a C program is allocated at
compile time whereas non-static data is allocated at run
time, typically on the stack.