Definition of poor white trash in US English:

poor white trash

noun

US
informal, derogatory
  • Poor white people of low social status, especially when regarded as uneducated or uncultured. In earlier use, frequently in the language of African Americans of the southern United States.

adjective

US
informal, derogatory
  • Of, relating to, or characteristic of poor white people of low social status, especially when regarded as uneducated or uncultured.

Origin

Early 19th century. From poor + white trash. Compare slightly earlier poor white.