kiloliter, kilolitre (British) The kilogram is the only Système International (SI) base unit of measurement whose definition is still based on a physical prototype. The world's most accurate kilogram is a cylinder of platinum and iridium that was made in 1889. It is maintained at the Bureau International Des Poids et Mesures (BIPM) at Sèvres nea... Found on http://www.wordinfo.info/words/index/info/view_unit/1123/