To back an anchor Meaning, Definition & Usage

Definitions
  1. to increase the holding power by laying down a small anchor ahead of that by which the ship rides, with the cable fastened to the crown of the latter to prevent its coming home.
Definitions
  1. (Naut.), to lay down a small anchor ahead of a large one, the cable of the small one being fastened to the crown of the large one.

Webster 1913