backstop

noun
  1. 1

    A thing or a person put in the rear or in the back of something to reinforce, hold, support.

  2. 2

    A default arrangement that holds if all else fails.

  3. 3

    A wall or fence behind home plate.

  4. 4

    A catcher; the position of catcher.

  5. 5

    (rounders) The player who stands immediately behind the striking base.

  6. 6

    The longstop.

  7. 7

    The wicket-keeper.

  8. 8

    Something serving to bolster or support a cover story etc.

verb
  1. 1

    To serve as backstop for.

  2. 2

    To bolster, support.

Source: https://en.wiktionary.org/wiki/backstop