Meltdown is a term used to describe the condition of a person who under pressure or stress has reached a point where they can no longer cope and have 'snapped' or 'lost it'. They may become angry, tearful or over react in an emotional meltdown.
According to the PDA Association (201?)
"At the most basic level, a meltdown is caused by a feeling of being overwhelmed and a sense of loss of control, the child is no longer able to cope and the behaviours are an attempt by the child to regain some control over themselves, those around them, their environment or a combination of these. It is most helpful if these meltdowns are understood as panic attacks, rather than wilfully naughty or defiant tantrums."
"Although meltdowns are typically associated with children or young people with an ASD/PDA, the state of panic and acute anxiety that drives meltdown behaviour can still cause profound difficulty for adults with the condition as well. Whilst older children and adults may have learnt some coping skills and be better able to contain their behaviour, the potential for an internal meltdown to incapacitate an individual must not be underestimated. Equally, although adults may be more robust and may have developed improved self-regulation, it is entirely possible for them to experience a loss of control that is so great, it causes them to explode outwardly with challenging behaviours. A meltdown is a state of mind and acute anxiety, rather than a description of a type of behaviour. The behaviour, when it occurs, is merely an external expression of this internal meltdown."
Tantrum is a term used to describe an outburst of childish or petulant behaviour in which the person may become angry, tearful or over react in an emotional manner. However, a tantrum is not the same as a meltdown.
According to the PDA Association (201?),
"A child having a tantrum is likely to be very aware of who is watching and how they are reacting to their behaviour, tantrums tend to need an audience and are exploitative of those involved, seeking to manipulate a situation to their own ends. A child in a tantrum may act in a way to attempt to maintain a certain credibility with peers or adults, for example they may be oppositional but not wish to appear too immature. By contrast when in a meltdown a child is often very unaware of those around them and care little about what others think of their behaviour and be inattentive to how others react to it."
Please see Meltdowns, Tantrums and Autism Publications