Provided by: postgresql-client-9.5_9.5.25-0ubuntu0.16.04.1_amd64 

NAME
DROP_USER - remove a database role
SYNOPSIS
DROP USER [ IF EXISTS ] name [, ...]
DESCRIPTION
DROP USER is simply an alternate spelling of DROP ROLE (DROP_ROLE(7)).
COMPATIBILITY
The DROP USER statement is a PostgreSQL extension. The SQL standard leaves the definition of users to the implementation.
SEE ALSO
DROP ROLE (DROP_ROLE(7))