geosmin

noun

geo·​smin jē-ˈō-smən 

ˈjē-ō-

plural geosmins

: a volatile organic compound C₁₂H₂₂O that is formed especially by soil-dwelling bacteria (such as streptomyces) and aquatic cyanobacteria and that may contribute to the earthy, pleasant odor of petrichor or impart a disagreeable, musty taste and odor to drinking water and certain fish

In the test kitchen, we too have noticed a mysterious muddy flavor in some catfish and tilapia. … When the fish swim in the geosmin-rich water, they consume the compound as they ingest the algae.

—Cook's Illustrated

Geosmin can be detected by a human nose at miniscule concentrations, as low as just a few parts per trillion, [Kelley Dearing] Smith said.

—James Bruggers

Note: Geosmin is a tertiary alcohol having a hydroxyl group (-OH) attached to a carbon atom that has three other carbon atoms attached to it.

Examples of geosmin in a Sentence

Recent Examples on the Web

When raindrops hit dry ground and plants, the impact creates microscopic bubbles filled with geosmin and oils that rise into the air, pop and scatter into tiny particles that can then fill human nostrils. — Gregory Wakeman, Scientific American, 1 Oct. 2026

The compounds in the lake causing the odor are called 2-methylisoborneol, or MIB, and geosmin. — Taylor Croft, AJC.com, 20 Sep. 2026

Oils build up in rocks, leaves and other natural surfaces during spells of dry weather and the particles – some of which are known as geosmin – are released once they're hit by rain. — Lance Schulteis, jsonline.com, 24 Aug. 2026

Baffle walls slow the flow of water coming into the treatment plant and allow solids like MIB and geosmin to settle before entering the plant for easier treatment, Carpenter explained during a July 22, 2025, council meeting. — Briah Lumpkins, Charlotte Observer, 25 Feb. 2026

Word History

Etymology

Greek gē-, geō-, combining form of gê "earth" + osmḗ "odor" + -in entry 1 — more at geo-, anosmia

Note: Term introduced by the American biochemist Nancy N. Gerber (1929-85) and the French-born American biologist Hubert A. Lechevalier (1926-2015) in "Geosmin, an Earthy-Smelling Substance Isolated from Actinomycetes," Applied Microbiology, vol. 13, no. 6 (November, 1965), pp. 935-38.

First Known Use

1965, in the meaning defined above