Knuckleballs

noun

1. A pitch thrown with the ball gripped on the fingertips and released with no rotation, which travels over an unpredictable path to the plate due to micro-turbulence in the air.

   "Boston Red Sox pitcher Tim Wakefield is best known for his use of the knuckleball."

2. An event that is hard to predict.

   "Our vendor keeps throwing us knuckleballs."