viscous

adjective

vis·​cous ˈvi-skəs 

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

viscously adverb

viscousness noun

Synonyms of viscous

• thick
• sticky

Examples of viscous in a Sentence

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

Recent Examples on the Web

Dye stripped from photos by lacquer moves in viscous flows that seep into other areas of the composition. —Theo Belci, Artforum, 1 Feb. 2026

Curtis said Gulf Coast refineries are already equipped to handle the viscous Venezuelan oil since those refineries were built to process similar grades of oil from Canada and Mexico. —Matthew Adams, Fort Worth Star-Telegram, 28 Jan. 2026

Nikola Tesla’s bladeless turbine design relies on viscous drag rather than traditional blades to generate rotational motion. —Prabhat Ranjan Mishra, Interesting Engineering, 12 Jan. 2026

While heavy crude oil is what is predominantly being drilled for today, its viscous consistency and high levels of metals and sulfur mean extracting and refining this product is significantly more costly than its light crude counterpart. —Sasha Rogelberg, Fortune, 5 Jan. 2026

Word History

Etymology

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

First Known Use

14th century, in the meaning defined at sense 1

Rhymes for viscous

• discus
• viscus
• hibiscus
• meniscus

Kids Definition

viscous

adjective

vis·​cous ˈvis-kəs 

1

: having the characteristic of stickiness

2

: having or marked by viscosity

Medical Definition

viscous

adjective

vis·​cous ˈvis-kəs 

1

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

2

: having or characterized by viscosity

a viscous flow