The antonyms for the word "most upper-class" include words like plebeian, lowborn, common, and uncultured. These words imply a lack of sophistication or refinement and suggest a lower social standing than those who are considered upper-class. While the upper-class is associated with wealth, education and power, the opposite end of the spectrum is characterized by simplicity, lack of education, and poverty. Antonyms play a crucial role in helping us understand the true meaning of a word by providing us with a contrasting view. In doing so, we can get a better sense of the word's scope and implications.