To cover parts of a building (often the windows) with wooden planks. That hurricane is bearing down on us, so we need to leave town as soon as we finish boarding up the windows. I can't believe someone finally bought that old, abandoned house—it's been boarded up for years.

Covered with wooden planks (especially over the windows), as of an abandoned building. I can't believe someone finally bought that old, boarded up house—it's been empty for years.