Wallpaper is thick coloured or patterned paper that is used for covering and decorating the walls of rooms.

If someone wallpapers a room, they cover the walls with wallpaper.

If you describe music, television, or art as wallpaper, you are critical of it because there is nothing interesting or difficult to understand about it, so people find it pleasant but do not pay much attention to it.

Wallpaper is the background on a computer screen.