high-key adverb 2adjective 1forms 4 adverb2 •(informal) In a conspicuous way. •(US, informal) Used as an intensifier; really.I'm highkey pissed at you right now. adjective1 •Characterized by light tones and the absence of a shadow.Details are tremendously important in composing an outstanding high-key photograph. — 1942 formsmore high key · more high-key · most high key · most high-key