fissure •\ˈfi-shər\• noun and verb noun: a long narrow depression in a surface noun: a long narrow opening noun: (anatomy) a long narrow slit or groove that divides an organ into lobes verb: break into fissures or fine cracks The word fissure has appeared in 113 New York Times articles in the past year, including on April 15 in the Green blog post "More on the Link Between Earthquakes and Fracking" by Henry Fountain: Scientists from the United States Geological Survey have cautiously weighed in on a subject that has sparked public concern in some parts of the country: spates of small earthquakes in oil- and gas-producing areas. In a report to be presented next week at a meeting of seismologists in San Diego, the scientists say that increases in the number of quakes in Arkansas and Oklahoma in the last few years are "almost certainly" related to oil and gas production. But in a summary of the report, they say they do not know if seismic activity is increasing because companies are taking more oil and gas from underground or because of "changes in extraction methodologies." One "extraction methodology" that has become increasingly popular, especially for natural gas production, is hydraulic fracturing, or fracking, in which water and chemicals are injected into wells under pressure to create fissures in the rock and unlock the gas. A report by a state seismologist in Oklahoma suggested that two minor quakes in January, about 50 miles south of Oklahoma City, may have been directly caused by a fracking operation. The Word of the Day and its definitions have been provided by Vocabulary.com and the Visual Thesaurus. Learn more about the word "fissure" and see usage examples across a range of subjects on the Vocabulary dictionary. Click on the word below to map it and hear it pronounced: