1
general::
1. Plunder or pillage; also, make a profit at someone else's expense, victimize. For example, Vikings preyed on the coastal towns of England, or The rich have been preying on the poor for centuries. [Late 1500s] 2. Hunt, especially in order to eat, as in Their cat preys on all the rodents in the neighborhood. [c. 1600] 3. Exert a baneful or injurious effect, as in Guilt preyed on his mind. [c. 1700]
American Heritage Idioms
2
general::
Phrase(s): prey on something
[for an animal] to feed on another animal as a matter of habit or preference. • Owls prey on mice. • Many birds prey on snakes., Phrase(s): prey (up)on someone or something
Fig. to take advantage of someone or something. (See also prey on something. Upon is formal and less commonly used than on.) • The people of that island prey on tourists and do not give them good treatment. • I really don’t want to seem to prey upon your kindness.
McGrawhill's American Idioms And Phrasal Verbs