noun The event of small airborne particles falling to the ground in significant quantities as a result of major industrial activity, volcano eruption, sandstorm, nuclear explosion, etc.
noun The particles themselves.
On 26 April 1986 the reactor number four at the Chernobyl Nuclear Power Plant located in the Soviet Union near Pripyat in Ukraine exploded. Further explosions and the resulting fire sent a plume of highly radioactive fallout into the atmosphere and over an extensive geographical area.
noun A negative side effect; an undesirable or unexpected consequence.
Psychological fallout in the shadow of terrorism
noun A declined offer in a sales transaction when acceptance was presumed.
noun The person who declines such an offer.
noun An impromptu guest used to fill in for another guest spot who is a no-show or who has cancelled last minute.