An initiative in which partners from two or more organizations have established a formal funding agreement to work toward the achievement of shared outcomes.
(Treasury Board of Canada Secretariat. "Results-Based Management Lexicon." Last modified February 25, 2010. http://www.tbs-sct.gc.ca/cee/pubs/lex-eng.asp.)
Two examples of horizontal initiatives are the Government of Canada's Drug Strategy and its Measures to Combat Organised Crime Initiative.