to crush, burden, unjustly keep in service or put down a person, group or entity by another person, group or entity, usually one that does not have the authority to do so;
e.g. Censorship is a way to oppress others, by taking away their right to free speech.
(verb)
to be made anxious or comfortable by something; to feel weighted down by something;
e.g. She was oppressed by some worry in the back of her mind.