Hail Mary, adj. — Green’s Dictionary of Slang

Hail Mary adj.

[a Catholic prayer for spiritual help. Note 1980s+ football/basketball jargon hail Mary, of a pass or throw, very long, often the last of the game, only likely to succeed through divine intervention]

(US) desperate, last-ditch.

1999		J. Maple Crime Fighter 141: In Brooklyn, we knew the idea would work; here [in New Orleans] we were throwing a Hail Mary pass.
2000		Lehr & O’Neill Black Mass 93: Their target would be the black Chevy—installing a bug in the car would be their ‘Hail Mary’ pass [...] 97: They’d thrown the Hail Mary and it had fallen woefully short.
2003		bjoconnorfla posting at MediaBistro.com 27 Jun. 🌐 OK, after agonizing, I took the advice here and emailed my Hail Mary pass around lunchtime today. I have no idea whether it will be received in time, since the editor was going out of town to do the final interview.
2003		Erik ‘One Little Wire’ posting at Moral-Flexibility.net 2 June 🌐 Be careful what you wish for (I wished that the damn car would run, even if it cost me my ‘hail mary’ fund...and in the end it did exactly that, almost to the dollar....).
2019		J.A. Struthers Appel 21: [of a punch] I squeezed my eyes shut and threw a Hail Mary left that connected with his eye and sent him reeling.
2022		G.M. Graff Watergate 598: The requested tapes represented ‘inadmissible hearsay,’ since Nixon himself wasn’t a member of the Watergate conspiracy. The argument was a clear Hail Mary pass .