[Lazarus] Compiling Python modules with Lazarus

[Mac Programmer]

I found the following in a makefile.fpc in the internet.

debpackage: all
	override COMPILER+=-dNODEBUG # passes -dNODEBUg to compiler options

Works for me... But can someone explain me in short what this command 
does and why?

For me looks like it adds -dNODEBUG to compiler commandline which is 
stored in COMPILER. What does override mean here?

sebastian