Second class and Unretentive

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

Unretentive and second class are semantically related. In some cases you can use "Unretentive" instead an adjective phrase "Second class".

Unretentive adjective - (of memory) deficient in retentiveness or range.

Second class and unretentive are semantically related. Sometimes you can use "Second class" instead an adjective "Unretentive".