Luke just stood where he was, holding onto the refrigerator door as if it were a lifeline. He was afraid he'd fall over if he let go. He did, at least, manage to close the door and lean his back against it while Dan did...whatever he was doing.
"I don't...Shine? What...What does that mean?" Luke had never heard the word before. Well, no. Of course he had heard the word. In relation to the sun, and things that were bright and reflective. Polishing something until it shined and the like. But the way Dan said it, in the context, Luke knew that wasn't what he meant. He just wasn't sure what he meant.
Clearly it had something to do with the ghosts. Or the ability to see the ghosts.