h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

For a person with an abuse history or any tendency to dissociate, a trigger is something reminds that person so much of a past event that ther person leaves here/now and goes to there/then. What GETS triggered could be an actual flashback (reliving, as though it were NOW, some previous event) or the feelings associated with some previous event.

Anything can be a trigger. A partial list would include an object, an action, a word, a smell and an attitude.

Once a person, and anybody closely associated with that person, knows his/her triggers, the easier they are to avoid. When a person who can be triggered knows how to identify that s/he IS triggered, it's not as difficult to get back to here/now. For that reason, if no other, knowing how to identify a trigger and tell when a person has been triggered is important for the person to whom this happens and anyone who cares about that person.

It is probably A Good Idea for a person who has just "gotten back" from being triggered to eximine WHAT the trigger was and WHY is was a trigger. All the better to avoid that trigger or to avoid being as triggered by the same thing in the future.