Mad Manic Laughter. When your bodies nervous system sidesteps your brain and you break out into laughter at inappropriate times. It becomes impossible to stop and the more you try the more manic the laughter becomes.
Can also be linked to a wicked laugh when you are about to do something bad but in your mind funny.
Whilst watching my friend in the school play during a particular serious piece, I was suddenly seized with an uncontrollable desire to laugh. I tried to stop but as my body shook I let out a loud snort and had to leave the room I was in a state of MML!