prey on somebody/something phrasal verb ( see also ↑ prey )
1 . if an animal or bird preys on another animal or bird, it hunts and eats it ⇨ predator :
Cats prey on birds and mice.
2 . to try to deceive or harm weaker people:
religious cults that specialize in preying on young people
3 . prey on sb’s mind to make someone worry continuously:
The accident has been preying on my mind all week.