...into holding that skill until either you run out of mana, get sealed, or something otherwise forces you to stop.
For example, if you steal Rapid Fire, place it into a macro, and use said macro, you will stand there in place and shoot until you can't shoot anymore.
Having the skill set to another key normally to activate and deactivate the skill does not free you from being locked into the skill.
If anyone is wondering how I even ran into this one, had Aria Amour and Sharp Eyes in a macro, totally flipped out on me when I switced it to Rapid Fire. :p