extinctionist noun 2adjective 1forms 3 noun2 •An advocate of extinctionism. •A player who plays a roguelike game with the additional challenge of killing all creatures to extinction. adjective1 •Relating to extinctionism.Hamas has embraced the nihilism of the suicide bomber, of rockets fired blindly into towns, and the nihilism of the extinctionist policy towards Israel. — 2011 formsextinctionists · more extinctionist · most extinctionist