This expression means betrayed or cheated. It originated in the Mississippi region of the USA during slave trading days. Slaves who caused trouble were sold from the northern slave states into the much harsher conditions on plantations in the lower Mississippi. The earliest reference to the phrase in print is from 1837. The figurative use of the saying began in the early twentieth century.

Übersetzung:

verraten und verkauft worden sein

Gegenteil(e)

The opposite of "to be sold down the river" is "to put in a good word for somebody".

Synonym(e):

You could also say: to be cheated.