Found this on another website and thought it was interesting. Here are some characteristics of a temper tantrum, versus an autistic meltdown:
"A temper tantrum is very straightforward. A child does not get his or her own way and, as grandma would say, "pitches a fit." This is not to discount the temper tantrum. They are not fun for anyone.
Tantrums have several qualities that distinguish them from meltdowns.
* A child having a tantrum will look occasionally to see if his or her behavior is getting a reaction.
* A child in the middle of a tantrum will take precautions to be sure they won't get hurt.
* A child who throws a tantrum will attempt to use the social situation to his or her benefit.
* When the situation is resolved, the tantrum will end as suddenly as it began.
* A tantrum will give you the feeling that the child is in control, although he would like you to think he is not.
* A tantrum is thrown to achieve a specific goal and once the goal is met, things return to normal."
"* During a meltdown, a child with autism does not look, nor care, if those around him are reacting to his behavior.
* A child in the middle of a meltdown does not consider her own safety.
* A child in a meltdown has no interest or involvement in the social situation.
* Meltdowns will usually continue as though they are moving under their own power and wind down slowly.
* A meltdown conveys the feeling that no one is in control.
* A meltdown usually occurs because a specific want has not been permitted and after that point has been reached, nothing can satisfy the child until the situation is over."
My only disagreement with this is that I have definitely known kids with autism who would throw true temper tantrums. The intention was very definitely to manipulate. I've had other parents of kids with autism tell me the same thing- many of these kids are "capable" of using tantrums (that appear similar to meltdowns) to try and get their way.