adjective
1.
( disapproving ) ( of a person ) less important than other people :
Older people should not be treated as second-class citizens .
2.
of a lower standard or quality than the best :
a second-class education
3.
[ only before noun ] connected with the less expensive way of travelling on a train, ship, etc. :
second-class carriages / compartments / passengers
4.
[ only before noun ] (in Britain) connected with letters, packages, etc. that you pay less to send and that are delivered less quickly :
second-class letters / stamps
5.
(in the US) connected with the system of sending newspapers and magazines by mail
6.
[ only before noun ] used to describe a British university degree which is good but not of the highest class :
Applicants should have at least a second-class honours degree.
► ˌsecond ˈclass adverb :
to send a letter second class
to travel second class