A person or thing that compels or forces; one who exercises compulsion.
From Latin 'compulsitor', an agent noun derived from 'compellere' (to drive together, compel), from 'com-' (together) + 'pellere' (to drive). The '-tor' suffix creates an agent noun.
This is a beautifully logical Latin creation—just as 'compel' means to force, a 'compulsitor' is 'one who compels,' yet it's so rare that most English speakers have never encountered it, showing how many perfectly grammatical words simply fall out of use.
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