Dymaxion is a coined word from the words "dynamic", "maximum", and "ion".  It was conceived of by a friend of Buckminster Fuller, and he adopted it and 4-D ("fourth dimension") for many of his projects, including the Dymaxion 4-D House, the Dymaxion Car, the Dymaxion Deployment Unit (war-relief housing), the Dymaxion Dwelling Machine (An improvement on the Dymaxion 4-D House), etc.

The dymaxion was also Fuller's name for the cuboctahedron or heptaparallelohedron, a quasi-regular uniform Archimedean polyhedron.  It's discovery is ascribed to Plato, technically making it a Platonic solid, although it does not meet the geometric requirements for such, as it's faces are not all equivalent.  A dymaxion also defines the shape of a cubic close packing of spheres.

Fuller used 4-D to refer to the planes generated in a tetrahedronal coordinate system which defines volume by four rays emanating from a singly point.  Fuller claimed that this defined and used space more efficiently.

Buckminster Fuller is best known today for his work on the geodesic dome, and construction and structure was the are he was most active in, although he received 26 patents in a wide variety of fields.  For more information about Buckminster Fuller, geodesics, or any of his other ideas, please visit The Buckminster Fuller Institute.