Mushrik

And do not marry mushrik women until they believe, for a believing bondmaid is better than a mushrik woman, even though you may admire her.

A person can have committed shirk in their lifetime and still find forgiveness (especially by saying the Shahada and becoming a Muslim). The concept is that if one dies in this state (as a mushrik, an idolator, one who engages in and does not repent shirk), there is no forgiveness.