unilateralist adjective 1noun 1forms 3 adjective1 •Supporting or advocating unilateralismYet he emerged as the driving force for the administration’s unilateralist policies. — 2009 noun1 •A supporter of unilateralism.“I am the last of the standing unilateralists,” Mr. Oren declared in a lecture in March at Georgetown University, where he was a visiting professor in Jewish studies until being named ambassador. — 2009 formsunilateralists · more unilateralist · most unilateralist