Definitions for "XBM"
(X Bit Map) A simple image format. XBMs only appear in black and white and you will find them in-line in HTML documents
The it ap format was designed specifically for small icons. It is in simple ASCII and only supports monochrome. It is supported on many platforms and most browsers. It is not space efficient, but because it is always used for small images, this is usually not a problem. Historically it is the original World-Wide Web image format; the others came along later.
X Windows Bitmap