Wild guess

• Very uncertain venture
• Lanky drunk crossing hotel? That’s unlikely
• Outside chance

Wikipedia Word definitions in Wikipedia
Long Shot is a 1939 American horse racing film directed by Charles Lamont . The film is also known as The Long Shot .

WordNet Word definitions in WordNet
n. a venture that involves great risk but promises great rewards a contestant that is unlikely to win

Wiktionary Word definitions in Wiktionary
alt. 1 (context idiomatic nautical English) Something unlikely; something that has little chance of happening or working. The term arose from the accuracy of early ship guns, which were effective only at close range and unlikely to hit the mark at any great ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
in the figurative sense of "something unlikely," 1867, from long (adj.) + shot (n.). The notion is of a shot at a target from a great distance, thus difficult to make. Cinematic sense is from 1922.