From Guild Wars Wiki
A fizzle is the term used to describe when skill activation begins, but that skill does not successfully finish. A fizzle is the opposite of an execute or successful execution. The reasons for a skill fizzling are varied:
- Interrupts are a common cause of fizzles. Generally caused by another player or enemy NPC using an interrupt skill. Interrupts generally discharge the skill, forcing the user to wait for recharge or longer to use it again.
- Cancellation is another common cause of fizzles. Attempting to move during a long activation time or pressing the escape key will cancel the skill causing it to fizzle. Cancels do not discharge the skill.
- The target becoming invalid during casting will also fizzle a skill, also known as fail, though the fizzle will not occur until the casting time is complete. This is frequently caused by the target dying during activation, but can also occur in the opposite: the target was already resurrected before a resurrection skill is complete. This does not discharge the skill.
- If the skill becomes disabled while it is being activated via Blackout or a similar skill, also known as fail, will fizzle.
- Fizzles are signaled in the game by a clicking or chirping sound, audible to all in the vicinity of the skill user, as well as a white "falling sparks" visual effect placed above the head to override any activation symbol that may have been there.