Common MacOS resource fork data type short for color icon. Not to be confused with icl4, icl8, ics4, ics8, or icns resources which are the 4, 8, and 32 bit icons used in the MacOS Finder. cicns are used internally to many applications, usually as decorations for dialogue boxes (such as alert warning symbols, and other superfluous dialogue identification). They are however as often as any other use, used for game sprites.