Meaning of yellow rain

yel'low rain'

Pronunciation: [key]
  1. small, powdery yellow deposits containing the fungal toxin tricothecene, found on leaves and other surfaces in Southeast Asia and Afghanistan in the early 1980s and alleged by some to be a chemical weapon disseminated by air but claimed by others to be pollen-containing bee excrement contaminated by fungus.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.