Hail Mary

1 :  a Roman Catholic prayer to the Virgin Mary that consists of salutations and a plea for her intercession

2 or less commonly Hail Mary pass :  a long forward pass in football thrown into or near the end zone in a last-ditch attempt to score as time runs out —often used figuratively The only potential cure is a stem-cell transplant, when you take somebody else's immune system and put it into yours. But right now that's kind of a Hail Mary pass. — Douglas Cote, quoted in Bicycling