First class and With-it

First class noun - Mail that includes letters and postcards and packages sealed against inspection.

With-it and first class are semantically related. In some cases you can use "With-it" instead an adjective phrase "First class".

With-it adjective - Keenly aware of and responsive to the latest developments especially in fashion and entertainment.

First class and with-it are semantically related. Sometimes you can use "First class" instead an adjective phrase "With-it".