Which figure of speech is used in this text?
For the time being, certainly, it had been found necessary to make a readjustment of rations (Squealer always spoke of it as a "readjustment," never as a "reduction") . . .
—George Orwell, Animal Farm

 - euphemism
 - antithesis
The text uses a euphemism, a polite or indirect expression that is used to de-emphasize an unpleasant topic.
A readjustment of rations is an indirect way of saying that food rations would be decreased.