To prey on ∨ upon Meaning, Definition & Usage

Definitions
  1. . (a) To take prey from; to despoil; to pillage; to rob . Shak. (b) To seize as prey; to take for food by violence; to seize and devour. Shak. (c) To wear away gradually; to cause to waste or pine away; as, the trouble preyed upon his mind.

Webster 1913