Definition of yellow rain in English:

noun

• A toxic yellow substance reported as falling in SE Asia, alleged to be a chemical warfare agent but now believed to consist of contaminated bee droppings.

  ‘Reports in the 1970s of Yellow Rain, alleged chemical/toxin weapons attacks in Southeast Asia and Afghanistan, sparked the first large-scale investigation conducted by the United States into allegations of chemical and biological weapons (CBW) use.’

  ‘The debate goes on for some time until an alternative explanation for the Yellow rain was presented, namely bee droppings.’