triggered == used. I can't remember now whether this valid for all triggers or not, but for example: on de_vertigo when you falling you touch invisible trigger that trigger (use) ambient_generic entity that emit sound.
(i'm not mean actual "+use" command but game engine's pfnUse).
But here is the problem: FM_Use is never called. It's not a bug (search for more info in this issue if interested).
EDIT: It may be that i messed the "triggered entity" term. I assumed that it is the trigger entity that is triggered the other entity (not the other entity that is triggered the trigger).