Backstop

[Luis Fok]

A thing placed at the rear of something as a barrier or support.

[Rihanna]

If your subway stop is full of commuters, and the [trains] [pulling in] are full, you get on a train going in the opposite direction in order to board one stop earlier. Guaranteeing yourself a spot [on the train].

[Donald Trump]

Backstop Solutions offers cloud-based productivity solutions for institutional investment firms and alternative asset managers. A software product by Backstop Solutions Group

[Gregory]

A person or thing placed at the rear of or behind something as a barrier, support, or reinforcement.

[Greta]

(in rounders) a player who stands directly behind the player from the opposing team who is trying to hit the ball, and attempts to catch the ball after it has been thrown if the person does not hit it