'Long Day's Journey' is a phrase that has been used in literature and popular culture to describe a long, arduous journey. The term is often used to describe a difficult journey that requires great effort and perseverance. In this crossword, the solution for the term 'LONG DAY'S JOURNEY' is 'TREK, ' which is a noun meaning a long and difficult journey, usually involving walking. This term is often used to describe a journey that requires physical and mental strength, as well as determination.