Axiom is  a general purpose Computer Algebra system. It is useful for research and development of mathematical algorithms. It defines a strongly typed, mathematically correct type hierarchy. It has a programming language and a built-in compiler.
Polybutylene is simply a type of plumbing material that was manufactured between the late 70's and early 90's. It is thought that it was installed in over 6 million homes during that time period.
Lead is a chemical element with the symbol Pb and atomic number 82. The symbol for lead, Pb, comes from the Latin name for the metal, plumbum. The English words plumbing and plumber are derived from this Latin name. Lead is a soft, malleable, ductile (drawn out into a thin wire) and heavy metal.