From Longman Dictionary of Contemporary Englishnot a pretty sightnot a pretty sightUNPLEASANTvery unpleasant to look at – sometimes used humorouslyAfter a night’s drinking, Al was not a pretty sight. →pretty
Examples from the Corpus
not a pretty sight• Are you sure you want to come in? It's not a pretty sight.• Afterwards I visited the boys and they were not a pretty sight.• All directors, including Spielberg, grow up, and in this film the result is not a pretty sight.• He is not a pretty sight.• What these portraits give you is a glimpse of Lowry's psychic state, and it's not a pretty sight.• It's not a pretty sight to finish in a classicfire and fall position.• It is not a pretty sight to see people so hurt.