Learner's definition of POSTAL
always used before a noun
: relating to or involved in the sending, handling, and delivery of mail
postal workers [=post office employees]
Postal rates are going up.
The city worked to quickly restore postal service.
go postalUS, informal
: to suddenly behave in a very violent or angry way
She suddenly went postal and started yelling at the customers.
If he calls me this late again, I'm going to go postal on him.