Degrowth is the literal translation of 'decroissance', a French word meaning reduction. Launched by activists in 2001 as a challenge to growth, it became a missile word that sparks a contentious debate on the diagnosis and prognosis of our society. 'Degrowth' became an interpretative frame for a new (and old) social movement where numerous streams of critical ideas and political actions converge. It is an attempt to re-politicise debates about desired socio-environmental futures and an example of an activist-led science now (...) consolidating into a concept in academic literature. This article discusses the definition, origins, evolution, practices and construction of degrowth. The main objective is to explain degrowth's multiple sources and strategies in order to improve its basic definition and avoid reductionist criticisms and misconceptions. To this end, the article presents degrowth's main intellectual sources as well as its diverse strategies (oppositional activism, building of alternatives and political proposals) and actors (practitioners, activists and scientists). Finally, the article argues that the movement's diversity does not detract from the existence of a common path. (shrink)