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 made in flat color style
. This format was developed by Icons8 designer team and became immensely popular for use in web and mobile applications. Feel free to download this icon in PNG format for free, or unlock other formats for $5. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 6,200 icons, all in the same style and quality.