What does viscous mean?
Viscous is an adjective for a liquid or other substance that is thick, sticky, and resistant to flowing. In physics and engineering, it is used specifically to describe the effect of internal friction within a fluid, as in viscous drag or viscous damping. In ordinary descriptions, viscous can refer to a thick consistency, such as viscous honey, paint, or mucus. The word also has figurative uses for situations, relationships, or sentiments that seem slow-moving, difficult to disentangle, or excessively sentimental. Its scientific sense is distinct from simply describing something sticky: viscosity measures resistance to deformation and flow, while stickiness refers more generally to adhesion. Viscous is useful because it captures both the physical behavior of a substance and the familiar feeling of something dense, resistant, and hard to move.
adjectiveHaving a thick, sticky consistency or a high resistance to flow. Figuratively, it can describe something slow-moving, difficult to disentangle, or cloyingly sentimental.
- Having a high resistance to flow, especially as a liquid.
- Having a thick, sticky, or glutinous consistency.
- Figuratively, slow-moving, difficult to disentangle, or cloyingly sentimental.
"The oil is so viscous that it barely flows through the narrow pipe."
"A viscous sauce clung to the pasta."
"The negotiations became so viscous that no meaningful decision could be made."
Viscous traces its name to Latin viscum, the sticky substance made from mistletoe or birdlime: the word literally belongs to a world of stickiness.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of viscous
Viscous comes from Latin viscosus, meaning “sticky” or “glutinous.” This adjective was formed from viscum, the Latin word for birdlime and mistletoe, both associated with a sticky quality. The English word entered use in the early seventeenth century and developed alongside related forms such as viscosity, viscid, and viscoelastic.
Related word forms
How viscous is actually used
In scientific and technical writing, viscous is standard for describing a fluid's resistance to flow. Its figurative uses are more literary and can suggest something cloying, emotionally manipulative, or resistant to change.
Easily confused with viscous
Both can mean sticky, but viscous usually emphasizes a liquid's resistance to flowing, whereas viscid more often means adhesive or prone to sticking.
Viscous is the adjective describing a substance, while viscosity is the noun naming the property of resisting flow.