Oppress, v. t. [imp. & p. p. Oppressed; p. pr. & vb. n. Oppressing.]
Etymology: [F. oppresser, LL. oppressare, fr. L. oppressus, p. p. of opprimere; ob (see Ob-) + premere to press. See Press.]
1. To impose excessive burdens upon; to overload; hence, to treat with unjust rigor or with cruelty. Wyclif. For thee, oppressèd king, am I cast down. Shak. Behold the kings of the earth; how they oppress Thy chosen ! Milton.
2. To ravish; to violate. [Obs.] Chaucer.
3. To put down; to crush out; to suppress. [Obs.] The mutiny he there hastes to oppress. Shak.
4. To produce a sensation of weight in (some part of the body); as, my lungs are oppressed by the damp air; excess of food oppresses the stomach.
Shades of meaning
Fernald has no entry of its own for oppress; he lists it under abuse.
Where he writes about it:
To persecute one is to ill-treat him for opinion's sake, commonly for religious belief; to oppress is generally for political or pecuniary motives. — from abuse
"Thou shalt not oppress an hired servant that is poor and needy," Deut. xxiv, 14. — from abuse