In the poem "Dream Deferred" by Langston Hughes, what does the term "dream deferred" mean?

Question

Also, in the US, what are some groups that have been exposed to predjudice?
I have some: African Americans, immigrants
Can anyone think of any others

Any dream that people put off achieving is a dream deferred. Hughes isn't specific, but the deferred dream could refer to equality among the races.

In addition to African-Americans and immigrants, the following often have been victims of prejudice: s and s, obese people, physically ugly people, laborers, homeless people, and women.

thank you!

The Irish and Germans have been objects of prejudice at different times and in certain places; also the Chinese and Japanese, especially during/after the California Gold Rush and WWII.