Russian roulette

Meanings

1. A deadly game in which a person loads a single bullet in the cylinder of a revolver, spins the cylinder so that the bullet's location is unknown, points the muzzle at his/her head, and pulls the trigger. In its most lethal form, played by multiple participants each of whom takes a turn until the weapon discharges.
2. Any activity, especially a needless one, that carries a high risk of death or disaster.

Etymology

From roulette, a game of chance involving a revolving wheel. The first description is apparently in "The Fatalist," an 1840 short story by Russian writer Mikhail Lermontov.