Open educational resources can be defined as ‘teaching, learning and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use or re-purposing by others. Open educational resources include full courses, course materials, modules, textbooks, streaming videos, tests, software, and any other tools, material or techniques used to support access to knowledge’

Definition from JISC Open Educational Resources (OER) frequently asked questions available from http://www.jisc.ac.uk/fundingopportunities/funding_calls/2008/12/grant14... (page last updated 12/01/09).  Also same definition here: http://www.ukcle.ac.uk/simshare/oer.html

Definition from https://openeducationalresources.pbworks.com/Glossary "Open Educational Resources are learning materials that are made freely available for use, remixing and redistribution."