Spool query output to file (SQLPlus)
To turn that off, use set heading off 

It then should result in: 

SQL&gt; select 'alter user '||USERNAME|| ' account lock password expire;' "Expiring Password" from dba_users where lower(username) in ('gunner','gunnersa','gunnerx3');

alter user GUNNER account lock password expire;


You probably also want to use: 

SET FEEDBACK OFF
SET TRIMSPOOL ON
SET TERM OFF
SET NEWPAGE 0


To get a "cleaner" SQL script when there are more than just three rows.