—n. 1. a wall, wire screen, or the like, serving to prevent a ball from going too far beyond the normal playing area.
2. Baseball.the catcher.
3. a person or thing that serves as a support, safeguard, or reinforcement: There were technicians on board as backstops to the automated controls.
—v.i. to act as a backstop.
—v.t. to act as a backstop to: The government agreed to backstop companies that invested in oil exploration.