[CentOS] rpmbuild --define | some rpm sorcerer around?

hi

how do you pass vars to rpmbuild for definition? eg

rpmbuild --define \'"${_definition2}"\'

I've been fiddling with ways to escape, but none is fricking working..
I mean, rpmbuild rushes to work(no errors nor failure) so if you try 
just the command line do not believe it, because later as it executes 
%if you will see process does not see these definitions.

many thanks, L