My all accounts, I’m a heavy sleeper, there are basically only 3 things that will reliably wake me up

My alarm clock
Having to pee
My dog throwing up or whining to go out (usually an indication that she’s gonna have diarrhea)

I sleep through my wife’s alarm going off (usually several alarms, she like to hit snooze,) showering, turning lights on, listening to podcasts while she gets ready, the sun coming up (I work partially overnight, I’m usually in bed by about 4 or 5 AM,) landscapers mowing the lawn outside my window, kids screaming at the nearby playground and school, fireworks, thunderstorms, construction (although I was not able to sleep through the siding repair I had done with a guy hammering on the wall directly behind my bed)

One time my wife was able to get me out of bed and stand me up so she could fix the sheets without me being fully awake.

When I was a kid my mom could vacuum in my room without waking me up.

I don’t know what this makes me, but I sleep through my phone going off and being touched (poked).

A light sleeper just means that your sleep is easily disturbed by small changes in your surroundings (like the turn of a doorknob, a car passing by outside, a text message to a phone on vibrate). There isn’t a strict criteria for it.

When I was a teenager I slept through a fire alarm once. I didn’t wake up until my mom walked in the room. I woke up before she said anything. Just her existing in my room for 0.5 seconds woke me.

So… idk.

Mirroring what others have said, often even heavy sleepers have sounds there sensitive to that wake them up immediately. I had someone crash on my couch one night. I knew they had to be up in the morning for work, so I set an alarm for myself to make sure they got up too (this is right around when smartphones were starting to become a thing, and it wasn’t really common to have alarms set on your phone, hence why I was going through the extra effort for them). I woke up and went over to try and wake them up. First it was a soft nudge in the shoulder, then a harder one, then a shake, then grabbing them by both shoulders and aggressively shaking them. I literally stopped to check their breathing and make sure they hadn’t died on me. My roommate came out during this and was also laughing and wondering if they had died. I really had to use the restroom, so said I was going to do that and then come back and give it another go. While I’m in there, I hear their phone go off and my roommate starts laughing hysterically. Apparently as soon as the tone went off on their phone, they sat upright, wide awake.