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late 14c., from Anglo-French viscous, from Late Latin viscosus "sticky," from Latin viscum "anything sticky, birdlime made from mistletoe, mistletoe," probably from PIE root *weis- "to melt away, flow" (used of foul or malodorous fluids); see virus.
viscous vis·cous (vĭs'kəs)
Having relatively high resistance to flow.