Ball Joint : A connection between two links in which the end of one member is partly spherical and fits into a corresponding cavity in the other member, thus allowing angular movement between them
Ministry of Business, Innovation and Employment, Glossary of terms and acronyms, Wellington, New Zealand 2010. http://wwwsosh.govt.nz/resources/glossary-u.shtml, (Occupn Hlth and Sfty - Brit) {530}