A boffer weapon is a padded, relatively safe mockup of a real sword, mace, staff, or whatever. It generally consists of a length of PVC pipe wrapped in insulation foam and duct tape, though more exotic materials can be used.
A boffer is a padded weapon used for simulated combat and are widely used in Live action role-playing games. The term "boffer" is not widely used outside of the USA - in Europe boffers are usually called latex weapons.