Crummy and Second class

Crummy adjective - Falling short of a standard.

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

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

Crummy and second class are semantically related in mediocre topic. You can use "Crummy" instead an adjective phrase "Second class".