Short for buckminsterfullerene, and part of a larger class of molecules known as as fullerenes, the third form of carbon. Any of a number of roughly spherical molecule formed of a large number of carbon atoms. The smallest and most common form of buckminsterfullerene is C60; it has 60 carbon atoms in a soccer-ball shape, but there are many variants. The third form of carbon. After atomic age visionary thinker and inventer R. Buckminster Fuller's building designs.