|a cause with no chance of success|
|a stew of meat, vegetables, potatoes, etc.|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
lost cause definition
A hopeless undertaking, as in Trying to get him to quit smoking is a lost cause. In the 1860s this expression was widely used to describe the Confederacy. [Mid-1800s] Also see losing battle.