Syntax:
REVOKE
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    FROM user [, user] ...

REVOKE ALL PRIVILEGES, GRANT OPTION
    FROM user [, user] ...

REVOKE PROXY ON user
    FROM user [, user] ...

The REVOKE statement enables system administrators to revoke privileges
from MySQL accounts.

When the read_only system variable is enabled, REVOKE requires the
SUPER privilege in addition to any other required privileges described
in the following discussion.

Each account name uses the format described in
http://dev.mysql.com/doc/refman/5.5/en/account-names.html. For example:

REVOKE INSERT ON *.* FROM 'jeffrey'@'localhost';

If you specify only the user name part of the account name, a host name
part of '%' is used.

For details on the levels at which privileges exist, the permissible
priv_type, priv_level, and object_type values, and the syntax for
specifying users and passwords, see [HELP GRANT]

To use the first REVOKE syntax, you must have the GRANT OPTION
privilege, and you must have the privileges that you are revoking.

To revoke all privileges, use the second syntax, which drops all
global, database, table, column, and routine privileges for the named
user or users:

REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...

To use this REVOKE syntax, you must have the global CREATE USER
privilege or the UPDATE privilege for the mysql database.

URL: http://dev.mysql.com/doc/refman/5.5/en/revoke.html

