Collins Chinese Dictionary Plus (3rd edition), 2011:
middle class
I n
▶ the middle class(es) 中产(產)阶(階)级(級) zhōngchǎn jiējí
II adj
(also: middle-class)
1 (sociologically) 中层(層)社会(會)的 zhōngcéng shèhuì de
2
(pej: bourgeois) 中产(產)阶(階)级(級)的 zhōngchǎn jiējí de