This ailment has many other names which are used loosely to define the same condition.  People, when describing ‘fits’, would use words like seizures or convulsions, epilepsy, paroxysms, apoplexy, etc.

Basically, in animals (I would not want to comment on the definition or symptomology in humans), a ‘fit’ or a seizure is a sudden and uncontrolled burst of activity which expresses itself as great excitability.  It is usually not a frequent occurrence (unlike ‘epilepsy’ which is recurrent).

The animal foams at the mouth (increased salivation) and chews vigorously (champing/grinding of …..