big if

plural big ifs

1. An unlikely but necessary condition.

   2004, Dale Brown, Dreamland: Strike Zone, HarperCollins, →ISBN, page 217, "If they believe us," said the admiral, "and that's a big if, then we're in a race with them to find this thing. Because if they grab it—"

   1 more example

   "If I were only old enough," said Kate, "and knew enough to teach a day-school, I would begin at once and save half of my money …." "Oh!" Edward replied, "there's a big if in the way."

   1868 Montgomery Schuyler, The Pioneer Church: Or, The Story of a New Parish in the West (Boston: Riverside Press, 1868), p. 2