Not sure how you reached the conclusion that white nationalism doesn't have a real meaning. Googling "white nationalism" gives plenty of results that indicate "white nationalism" is an ideology that promotes white supremacy and/or a whites-only nation/racial segregation.

To quote Merriam Webster:

"one of a group of militant whites who espouse white supremacy and advocate enforced racial segregation"

To be clear, I stated that I'd never heard the official definition and used context clues to come up with a running (incorrect) definition.

I am not of the opinion that white nationalism has no real meaning.