If something is considered to be 'a lost cause', then it is believed to have a high chance of failing, or it is not worth pursuing. Likewise, if a person is 'a lost cause', they are considered to have no chance of succeeding. This can often be used to joke about someone who might not be doing what everyone expects of them. For example, if a man stops hanging out with his friends because his new girlfriend takes up all his time, his friends might say, "There's no point asking John to come out tonight. He spends all his time with his girlfriend. He's a lost cause!"

1. Trying to keep a clean house with four young children living in it can be something of a lost cause!
2. I've tried countless times to help Adam but nothing seems to work. At this point I'm beginning to think that he is a lost cause.

1. The latest setback means completing the work on time is looking more and more like a lost cause.
2. Some of the customers you will capture at the beginning of the sales funnel are a lost cause and will never purchase your product.