I think that in the PTSD sense, a trigger is something that is directly related to our trauma. Anything not directly related to our trauma is considered a stressor.
That's a helpful distinction. The word "trigger" seems over-used. For healing, it's helpful to try to sort it all out. Lots of things tip me into a hyper or angry mode because I simply have dysregulation issues. I wouldn't call most of them "triggers"...but stressors that I handle sort of badly because my body simply mismanages all kinds of stress...even good stress sometimes.
As for "triggers", they are mostly related to body sensations and feeling like I don't have control (so like pain, being sick, anything unpredictable)...a therapist summed it up by telling me my body is my main trigger. The difference between regular stressors and these triggers is that I feel trapped, immobilized, and horribly stuck in all time (that's how it feels, though it doesn't make sense...I'm not in the present, but like scattered all over the place). I feel completely uncontained and yet I can't just curl up because I feel totally trapped. Trapped and yet blown to pieces.
I have very few visual flashbacks (if I do, it's like flashes of light, still highly sensory bits, or brief images from adult trauma...like stuck on my hand trying to reach for safety). Most of my re-experiencing involves body memories and physical sensations (major traumas were serious early medical and body-violating abuse). I'm usually alone but I can't handle people close to me...even light touch makes me sting all over, like I'm hitting a fire or being electrocuted...highly charged like that.
I can't avoid my body anymore so am working on tolerating a huge range of experiences. If I have to face bad triggers head on, I do my best to breathe and over-focus on something present. But certain pains or sensations make me go totally numb and I feel like I'm floating (this happened during a uterine biopsy). I assume my doc saw me checking out because I remember her saying my name a lot. Thankfully I don't need uterine biopsies daily. But to help with any medical or invasive-like procedure, I've gotten good at asking lots of questions. I also stick with doctors who aren't rush-rush, who explain what options are and give me choices, and then explain what will happen. I also allow myself a hide-out place and period of time afterwards.
Sucks because I can't get away from my body, so it would seem. But I did for a long time...numbness, existing outside my body, etc. To be healthy I have to pay attention to various sensations and cues and learn how to feel myself connected/within my body.
I don't get too hung up on terms. I call my ugly episodes "meltdowns" and they all involve time and self distortions. It helps to recognize what's going on before I get to too deep...then I have strategies for keeping present and feeling mobile and less trapped.