What does locked password mean in CentOS?

Question

Passwords

Good day.
The question is probably stupid, but I can not find a clear definition of what a locked password is
. The essence of the question.
I inherited a server with postgresql
And just in case I wanted to know if there is a password on the postgres user.
For this I did the following.

[[email protected] ~]# passwd --status postgres
postgres LK 2016-07-27 0 99999 7 -1 (Password locked.)

However, if you do

[[email protected] ~]# su postgres
bash-4.1$

that comes under this user without problems.
Hence the question, what does locked password mean? I can't find a clear definition.
And does this mean that this user has a password?

Answer 1

man passwd

-l, --lock
           Lock the password of the named account. This option disables a password by changing it to a value
           which matches no possible encrypted value (it adds a ´!´ at the beginning of the password).

Generally speaking, usually a toaster question assumes that the relevant mana has been read...