Low-down and Second class

Low-down adjective - Not following or in accordance with standards of honor and decency.

Second class and low-down are semantically related. In some cases you can use "Second class" instead an adjective phrase "Low-down".

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

Low-down and second class are semantically related. Sometimes you can use "Low-down" instead an adjective phrase "Second class".