postal
Concise Oxford English Dictionary © 2008 Oxford University Press:
postal/ˈpəʊstl/
▶adjective
- 1 relating to the post.
- 2 chiefly Brit. carried out by post: a postal vote.
– phrases
go postal US informal go mad, especially from stress. [with ref. to cases in which postal employees have run amok and shot colleagues.]
go postal US informal go mad, especially from stress. [with ref. to cases in which postal employees have run amok and shot colleagues.]
– derivatives
postally adverb.
postally adverb.
'postal' also found in these Oxford entries:

