A trigger is something (sound, smell, word/phrase, person, situation) that reminds you of a negative experience. A person might be walking down the street, and smell fresh cut grass, which could trigger them - they would have an automatic response, such as a panic attack, a flash back etc. So it's not specific to the response in you, it's just describing a reminder. You can dissociate in response to a trigger, such as into another alter, but it doesn't mean that you always will. A lot of the time I will be triggered and one of my little ones will come out, who are vulnerable. It's difficult to deal with. I have to try and come up with strategies to help them to know they are safe.
xo
IJ