touch and go

Extremely uncertain or risky, as in It was touch and go after the surgery; we were not sure he'd survive it, or It was touch and go but they finally gave me a seat on the plane. This idiom implies that a mere touch may cause a calamity. [Early 1800s]

A risky situation. There are times when a ship's captain or pilot must pick the vessel's way through such a narrow channel that its sides might well scrape against rocks or other potentially destructive hazards. Nevertheless, the captain or pilot had no other choice. That is to say, the ship might touch but it had to go regardless of the risk. Hence, this expression for an uncertain enterprise. A literal application of the phrase is an airplane's touching down on the runway, but then immediately lifting off because a normal landing would be dangerous. Pilots practice the maneuver when learning to fly.