Definitions of fully qualified domain name on the Web:

• A fully qualified domain name (FQDN), sometimes referred to as an absolute domain name, is a domain name that specifies its exact location in the ...
  en.wikipedia.org/wiki/Fully_qualified_domain_name
• The unique name of a network entity, consisting of a hostname and a domain name that can resolve to an IP address. ...
  pronto.jrc.it/manual/glossary.html
• A fully-qualified domain name (FQDN) is that portion of an Internet Uniform Resource Locator (URL) that fully identifies the server program that ...
  https://wfsm.webfarm.co.nz/kb/glossary/
• FQDN is the full name of a system, rather than just its hostname. For example, cisco is a hostname and www.cisco.com is an FQDN.
  www.cisco.com/en/US/docs/net_mgmt/broadband_access_center/30/administration/guide/Glossary.html
• A domain name that extends all the way back to root. Often written as FQDN www.google.com. is an FQDN.
  snaptec.co.za/page.aspx