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Definition of foamy virus in US English:
foamy virus
noun
VirologyAny of a group (now the genus Spumavirus) of retroviruses which infect a number of mammal species (including humans), and which induce the formation of giant cells with vacuolated cytoplasm in tissue culture, but appear to cause little or no disease in their natural hosts.
Origin
1950s; earliest use found in Proceedings of the American Philosophical Society. From foamy + virus, so called on account of the vacuolated cytoplasm of infected cells.
