Definitions of Web 2.0 on the Web:

• "Web 2.0" refers to what was perceived as a second generation of web development and web design. It is characterised as facilitating communication ...
  en.wikipedia.org/wiki/Web_2.0

• The second generation of the World Wide Web, especially the movement away from static webpages to dynamic and shareable content and social networking
  en.wiktionary.org/wiki/Web_2.0

• The use of World Wide Web technology and web design that aims to facilitate creativity, information sharing, and, most notably, collaboration ...
  www.anvilmediainc.com/search-engine-marketing-glossary.html

• A term that refers to a supposed second generation of Internet-based services. These usually include tools that let people collaborate and share information online, such as social networking sites, wikis, communication tools, and folksonomies.
  searchenginewatch.com/define

• Web 2.0 does not refer to any specific change in the technology of the Internet, but rather the behavior of how people use the Internet. ...
  www.twinity.com/en/glossary

• The transition of the World Wide Web from a collection of websites to a full-fledged computing platform serving web applications to end users.
  www.tvb.org/multiplatform/Multiplatform_Glossary.aspx

• A term describing the supposed second generation of web applications that encompass 'community' sites. Examples include wikis, social networking sites, blogs etc
  www.nitro-digital.co.uk/glossary.html

• A term used to describe a new generation of Web services and applications with an increasing emphasis on human collaboration.
  www.headland.co.uk/pages/glossary

• currently lacks a precise definition. It is true to say, however, that although Web 2.0 need not necessarily incorporate new technologies it is ...
  www.quantum3.co.za/CI%20Glossary.htm

• a term introduced in 2004 to characterize design patterns in a constellation of new generation Web applications which may provide an ...
  www.csa.com/discoveryguides/scholarship/gloss.php

• Web 2.0 (or Web 2) is the popular term for advanced Internet technology and applications including blogs, wikis, RSS and social bookmarking. ...
  www.informit.com/guides/content.aspx

• Really more of a marketing term than a technical one, “Web 2.0″ refers to applications that allow direct interaction between a website visitor ...
  blog.beacontechnologies.com/other-stuff/website-redesign-terms-you-need-to-know/

• Web 2.0 refers to the second generation of the Web, which enables people with no specialized technical knowledge to create their own websites, to self-publish, create and upload audio and video files, share photos and information and complete a variety of other tasks.
  www.capilanou.ca/help/active-cms/glossary.html

• A mix of technology and business process that facilitates conversational marketing.
  www.bottlepr.co.uk/glossary.html

• One of those "cool" terms that is batted around with little definition. It refers to the “second generation” Web, today’s WWW that is more interactive and participatory than the Web used to be. ...
  www.neubertweb.com/definitions.html