Laughing so hard that the voice box shuts down and the body jerks around in spasmatic efforts to make a noise.
Anneliese, watching from her bed, was in the middle of one of those spasms of SILENT LAUGHING that wrack your body with convulsions and render you unable to make a single noise. You're like a whacked-out mime immitating a gleeful chimpanzee who just threw a handful of faeces at someone from behind the bars at the zoo.
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