Syntax:
STOP SLAVE [thread_types]

thread_types:
    [thread_type [, thread_type] ... ]

thread_type: IO_THREAD | SQL_THREAD

Stops the slave threads. STOP SLAVE requires the SUPER privilege.
Recommended best practice is to execute STOP SLAVE on the slave before
stopping the slave server (see
http://dev.mysql.com/doc/refman/5.5/en/server-shutdown.html, for more
information).

When using the row-based logging format: You should execute STOP SLAVE
on the slave prior to shutting down the slave server if you are
replicating any tables that use a nontransactional storage engine (see
the Note later in this section). In MySQL 5.5.9 and later, you can also
use STOP SLAVE SQL_THREAD for this purpose.

Like START SLAVE, this statement may be used with the IO_THREAD and
SQL_THREAD options to name the thread or threads to be stopped.

*Note*:

In MySQL 5.5, STOP SLAVE waits until the current replication event
group affecting one or more nontransactional tables has finished
executing (if there is any such replication group), or until the user
issues a KILL QUERY or KILL CONNECTION statement. (Bug #319, Bug
#38205)

URL: http://dev.mysql.com/doc/refman/5.5/en/stop-slave.html

