vis·​cous | \ˈvi-skəs \

Definition of viscous 

1 : having a thick or sticky consistency : viscid viscous secretions viscous corn syrup

2 technical : having or characterized by a high resistance to flow viscous lava

Keep scrolling for more

Other Words from viscous

viscously adverb
viscousness noun

Synonyms & Antonyms for viscous


ropy (also ropey), syrupy, thick, viscid


runny, soupy, thin, watery

Visit the Thesaurus for More 

Examples of viscous in a Sentence

viscous syrup that takes forever to pour from a narrow-neck bottle

Recent Examples on the Web

At Lassen, where the magma is usually very viscous — kind of like a crystalline mush — new magma began lifting up toward the surface in 1914, rejuvenating the stagnant magma beneath the volcano, said USGS volcano scientist Mike Clynne. Rong-gong Lin Ii,, "A California volcano once obliterated a forest and propelled ash 280 miles. Experts say it offers a warning," 22 May 2018 Toward the end, the dancers clumped together and switched into a slow-motion mass, shape-shifting across the stage, with Stephanie Kim pulling away for a solo of a deliberate viscous quality. Laura Bleiberg,, "Barak Ballet at the Broad Stage: New moves for a company on the verge," 1 July 2018 The ionic liquid in his fuel cell is goopy, 10 times more viscous than water. Robert F. Service, Science | AAAS, "Ammonia—a renewable fuel made from sun, air, and water—could power the globe without carbon," 12 July 2018 Kapoho managed to survive for two weeks after the first eruption, but its fortunes changed when less viscous lava spilled out. Rong-gong Lin Ii,, "Hawaii’s Kilauea volcano destroys 35 structures; scientists say additional eruptions are likely," 8 May 2018 Some polymers used in the machines are notorious for irreversibly yellowing, flaking, and turning cloudy and viscous. Eve M. Kahn, New York Times, "No, Your Furniture Shouldn’t Drip or Burst," 2 Mar. 2018 MIAMI - One day in late May 2016, Roger Stone - the political dark sorcerer and longtime confidant of Donald Trump - slipped into his Jaguar and headed out to meet a man with a Make America Great Again hat and a viscous Russian accent., "Trump associate Roger Stone reveals new contact with Russian national during 2016 campaign," 17 June 2018 The molokhia leaves are also known as jute or Jew’s mallow (a bitter green somewhere between spinach and sorrel that can get viscous, similarly to okra, when cooked). Chris Morocco, Bon Appetit, "This Braised Chicken Soup with Greens Recipe Is PERFECT for Spring," 21 May 2018 These guys contain magma (i.e., underground lava) that is quite thick and viscous. Anna Rothschild, Washington Post, "Here’s why some volcanoes are more explosive than others," 10 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'viscous.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of viscous

14th century, in the meaning defined at sense 1

History and Etymology for viscous

Middle English viscouse, from Anglo-French viscos, from Late Latin viscosus full of birdlime, viscous, from Latin viscum mistletoe, birdlime; akin to Old High German wīhsila cherry, Greek ixos mistletoe

Keep scrolling for more

Learn More about viscous

Statistics for viscous

Look-up Popularity

Time Traveler for viscous

The first known use of viscous was in the 14th century

See more words from the same century

Keep scrolling for more

More Definitions for viscous



English Language Learners Definition of viscous

of a liquid : thick or sticky : not flowing easily


vis·​cous | \ˈvis-kəs \

Medical Definition of viscous 

1 : having a glutinous consistency and the quality of sticking or adhering : viscid

2 : having or characterized by viscosity a viscous flow

Keep scrolling for more

Comments on viscous

What made you want to look up viscous? Please tell us where you read or heard it (including the quote, if possible).


playful or foolish behavior

Get Word of the Day daily email!

Test Your Vocabulary

Autumn Words of the Day 2018

  • a-top-down-image-of-road-through-an-autumn-forest
  • Which is a synonym of fugacious?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!


Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!