A long shot is something that is very unlikely to happen.
An attempt or effort that is not likely to be successful.
Little chance of winning.
1. I know it’s a long shot but can I have your number?
2. The stock was a long shot but I invested all my money, anyway.
3. Winning the lottery is always a long shot.
4. It might be a long shot but cutting the black wire always helps disconnect the circuit when I’m in doubt.
chance hit, fluke, hundred-to-one-shot, little chance, long odds, lucky shot, no chance, off-chance, one in a million, outside chance, poor bed, slim chance, small chance