BEASTLY BRIT. Meaning of BEASTLY BRIT. in English beastly Brit.informal■ adjective ( beastlier , beastliest ) very unpleasant. ■ adverb dated to an extreme and unpleasant degree.Derivativesbeastliness noun Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004