MACRO cancelqueuedspell

Stop the queued spell from casting.
 /cancelqueuedspell
== Usage ==
This command accepts secure command options. If at least one condition is satisfied, the spell casting queue will be cleared.
== Notes ==
* When you cast a spell in WoW, and you are in the middle of a combat action, the spell is queued up to be cast when that one is done, up to a maximum number of 1 spell. This feature was implemented to help players compensate for high latency. If you cancel your current spell, the queued spell is cancelled as well. This command lets you cancel the queued spell without cancelling your current spell.
* Added in patch 4.1.