Execute

From Guild Wars Wiki

An execute is simply a successful skill use: the target was verified, any cost was paid, any casting time was passed, the target is still valid, and now the skill applies its effect, its normal recharge, any after-cast effects, and the execute is complete.

This is a specific technical term, in most speech "I used the skill" implies the most common end result of success; exceptions such as "I started to use the Flaying Mindbender but canceled it" or "Joe Devourer interrupted my Signet of Particles!" would be stated directly.

A fizzle, being an unsuccessful skill use, is the opposite of an execute.