It's an icon with a paint bucket about halfway tipped over. There is liquid running out of the bucket because it is tipped partially over. There is a slash line running through the middle of the paint bucket starting at the top left through the bottom right.
This No Filling icon is a responsive icon. This means that it's optimized for four resolutions, from tiny 16x16 until highly detailed 80x80. The style comes from the latest Microsoft Office
, which makes it perfect for any Windows applications, in particular, those with ribbon toolbar control. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 16,000 icons, all in the same style and quality.