boundary layer

American  

noun

Physics.

1. the portion of a fluid flowing past a body that is in the immediate vicinity of the body and that has a reduced flow due to the forces of adhesion and viscosity.

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boundary layer British  

noun

1. the layer of fluid closest to the surface of a solid past which the fluid flows: it has a lower rate of flow than the bulk of the fluid because of its adhesion to the solid

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Etymology

Origin of boundary layer

First recorded in 1920–25

Example Sentences

Collected by gliders, floats and drifters, these instruments provide valuable information about the most turbulent region of the hurricane environment, called the boundary layer, where the air meets the ocean.

From BBC • Aug. 29, 2025

"We human beings are living in this boundary layer, so understanding and accurately modeling it is essential for storm forecasting and hazard preparedness," said author Qiusheng Li.

From Science Daily • Nov. 19, 2024

That boundary layer is dissipated by the moving air, increasing the pace at which your skin cools.

From New York Times • Jan. 12, 2024

That day, northerly cyclonic winds swept warm and dry continental air over a moist, cooler boundary layer on the Black Sea.

From Science Magazine • Nov. 17, 2023

Better, but— Harry beat it: glass, plastic, and a boundary layer of cold air, jetted down from the ceiling, in front of the background painting and back of the look-in window.

From Question of Comfort by Collins, Les