To defraud someone by giving them less change than they should be given after a transaction.
I got shortchanged! …I gave him $10 for a $5 item and he only gave me $1 back.
(by extension) To deprive someone of something for which they paid.
The elective class was easy, but in the end I was shortchanging myself.
To make disadvantaged by design.
Being proud of mistreating shortchanged "enemies" is a likely sign of class consciousness, as well as thinking or speaking ill of them.