pickblack day . black day {n.} A day of great unhappiness; a disaster. It was a black day when our business venture collapsed. Categories: add yours business disaster noun Source: A Dictionary of American Idioms 'black day' on video Black Day A Tribute To APS PESHAWAR STUDENTS | Short Film with Songs | Black Day APS | 16 December 2014 Black Day Black Day | 16 December 2014 | APS Attack sort: relevance, mode: exact match, q: "black day", maxResults: 4, videoEmbeddable: true, videoSyndicated: true, safeSearch: strict, type: video Subscribe to: American IdiomsEnglish Slang Discuss