Kmisho,
There is a language barrier affecting you and the person you are debating, I'm sure. Your definition of "objective" is in most cases quite sufficient. However, in discussing moral objectivism with a theist, the big difference is usually a meta-ethical question of the nature of objective morality itself. Most theists are moral realists who reject the notion of
ethical subjectivity.
To the theist, moral objectivity usually means that certain actions are right or wrong independent of human opinion. Not just that certain things are wrong today but ok 50 yrs ago or what have you, but they are wrong now, and always were wrong, and ever shall be wrong. They are wrong even if we do not have the knowledge that they are wrong.
For example, murder. A moral realist could say, based on the objective morality of God (for example), that murder will always be wrong. It will remain wrong even if society evolves and murder becomes acceptable. Even if mankind never discovered it was wrong, it is still wrong.
Of course, then the argument usually goes differently at this point, and the question arises how we know for certain what is right, and what is wrong, etc etc.
Anyway, I just wanted to point out a couple different ways of looking at moral obectivism and simply advise that often the atheist and the theist are not always speaking the same language.
Blessing