slingshot

Concise Oxford English Dictionary © 2008 Oxford University Press:
slingshot/ˈslɪŋʃɒt/

▶noun

• 1 chiefly N. Amer. a hand-held catapult.

  ■ a shot from a catapult.

• 2 the effect of the gravitational pull of a celestial body in accelerating and changing the course of another body or a spacecraft.

▶verb (slingshots, slingshotting; past and past part. slingshot or slingshotted) forcefully accelerate through the effect of gravity.