Plebeian and Second class

Plebeian adjective - Belonging to the class of people of low social or economic rank.

Second class and plebeian are semantically related In some cases you can replace phrase "Second class" with "Plebeian", this terms are similar.

Second class noun - Not the highest quality in a classification.

Plebeian and second class are semantically related in low topic. Sometimes you can use "Plebeian" instead an adjective phrase "Second class", if it concerns topics such as poor.