Meltdown

I would only add that where you read in other responses, where you the term 'child' is used, that you also consider how the same dynamics also typically apply to teens and adults with ASD.

I'd call that shut down too and I had more of those than melt downs as a kid. Apparently, I'd just freeze and become non-verbal and unresponsive.  Melt down, in whatever form, everyone there notices, shut downs rarely are noticed. The melt down/shut down thing can take many forms.

Very, very rarely do I have them, but I have been known to have puddle of tears type melt downs - uncontrollable anguished crying you often can't identify the cause for and just won't stop.  Mercifully, I can feel that coming and generally manage to get away by myself.  In medical situations, I can get some pretty dramatic 'flight' or 'explosion' type meltdowns which are sensory/fear driven.  Sadly, they cause problems because someone is about to or has just done something to me and there's no escape.  Those are getting worse as I get older.

I’m not sure if I’d call it a meltdown, but for me it’s like all of my insides want to explode. I stim more, rocking or if I’m not at home I’ll dig my nails into my skin and clench my teeth and bounce my feet, it’s it’s really bad I’ll start rocking despite not being at home. But I don’t really cry or scream or lash out at people. That’s possibly because as a kid I grew up in a bad place and if I lashed out I’d be screamed at and threaten so I learned to scream on the inside and hold everything in until I felt as if I was being pulled apart. I’d often not be able to speak even when words to retort with were racing through my head. I’d just open and close my mouth “like a dying fish” according to my mom. 

Like I said, I’m not sure if that qualifies as a melt down. And I haven’t been diagnosed with autism yet, so for all I know that could be a normal anxiety attack.

A meltdown for me is when I literally cannot cope with anything anymore, like I just stop and can't go on. I'm trembling, sometimes can hardly breathe and feel faint and sick. It's like so much is happening and it fries me. I become silent, won't talk. I cry. I scream. Hit and throw things. I just lose it and need to be left alone until I recover. This happened to me a lot when I was little and growing up, luckily it doesn't happen to me as much now. It still can happen but only when something big happens and overwhelms me. That for me is a meltdown.

A meltdown for me feels like overwhelming discomfort. I don't really want to call it pain, but it's like my brain just can't process anything else, and I get so angry when people expect me to (when they talk to me or touch me). It feels like I need to escape my skin, and like I just can't continue feeling that way because every action after it is overwhelming, over stimulating, and exhausting. This means my reaction is either anger and frustration, or a complete shutdown. A shutdown means I will become unresponsive, unable to speak, unable to communicate, and unable to think too much. I'll just retreat until I can take a nap. A meltdown for me is just me being really frustrated in public and then getting to a space where I am safe and then sobbing uncontrollably. It normally is really really exhausting though in public to try to be okay because everything is triggering it more.

Ive constantly said shut up.  Out loud sometimes.  Shut up to my stupid thoughs, my stupid worries.  Ive done it since i was about 16.  When people drone on...."shut up" is recycling in my head all the time.  Everyday.  I dont even notice it anymore until youve just posted that

As Lateralus says, everyone is different. Until I realised that I was most likely autistic I didn't equate prior experiences with meltdowns. I'd been aware of sensory issues for a while and assumed this was Misophonia. On occasions when it was really bad or I couldn't escape whatever was going on I'd be thinking "Shut up, Shut up, Shut up", or even saying it out loud, hands clenched into fists etc. A couple of times I've broken things that I've been holding. I'm much better at identifying when I'm close to meltdown now though and mitigating it before it gets that bad.   

A tantrum is a controlled rage where the person is intentionally trying to get their way by getting attention. It usually stops if the person gets their way or after a length of time without intervention and they can get embarrassed by others seeing their tantrum.

Whereas a meltdown is triggered by a sensory overload which is totally out of the persons control. They can be sometimes prevented if you are aware of their triggers Sounds and noises, light, crowded spaces, even smells can trigger a meltdown. They won’t usually resolve on their own, and ear defenders, quiet places with little or no stimulation and weighted blankets are needed to help a person having a meltdown. 

yes they can vary in severity and can manifest in different ways.. Without knowing the events leading up to the laying on the floor it is hard to say whether it is meltdown based or not. but hopefully with the above info you may have an idea which it is.

For me, thats a shutdown......  A meltdown for me would be being visably aggitated, trembling, crying.....trying to break my phone in half, punching hard wood to inflict damage to my hands and wandering off (sometimes in bare feet) luckily I dont do that now.

But everyone is different.