1.The radioactive particles that settle to the ground after a nuclear explosion.
2.The falling to the ground of radioactive particles lifted into the atmosphere by a nuclear explosion.
3.An incidental or unexpected effect, especially one which is undesirable, consequent to an event or process;; usually used only in the singular; as, the fallout from the disclosure of the Lewinsky tapes made trouble for the President for months after the event; fallout from the stock market crash caused property prices to decline in the New York area.
4.(Med.) One selected from a group by some criterion. (cant) "Corrective action was taken in 97 of the 418 from 3,787 patients at risk."
5.One who fails to maintain the same pace as and lags behind a group of which s/he is a member. (cant) "The executive officer's group noted all by name and policed them into a group to complete the run at a slower pace."
