The mysterious, misunderstood threat that propels the classic
film noir Kiss Me Deadly; it turns out to be a suitcase of a glowing, uncontrollable radioactive substance.
The great whatsit need not name anything specific: it refers to any nebulous but presumably devastating threat that becomes an obsession
for an individual or even an entire nation, regardless of its materiality. Much of its terror comes by way of implication. Examples include the communists of the 1950s, the JFK conspiracy
and Weapons of Mass Destruction