nostril
noun
nos·tril ˈnä-strəl 
1
: either of the external nares
broadly : either of the nares with the adjoining passage on the same side of the septum
2
: either fleshy lateral wall of the nose
Example Sentences
My left nostril is stuffed up. She left in a rage, her nostrils flaring.
Recent Examples on the Web Putting a finger on or inside your nostril can inadvertently transmit any bacteria or viruses on that finger into your nose, creating the perfect scenario for an infection, according to the US National Library of Medicine. 
Maggie O'neill, Health.com, 22 Sep. 2021 Manson allegedly returned a second time, covering one side of his nostril and blowing in Fountain’s direction. Michael Casey, USA TODAY, 18 Aug. 2021 The test -- the Pixel by Labcorp -- is designed for users taking a swab of their nostril and then sticking it into a solution. Matthew Vann, ABC News, 12 Apr. 2021 Failing and then flailing, a bored Reardon put a magnet in his nostril. Steve Mirsky, Scientific American, 26 May 2020 Heading into the D-Day remembrance weekend this year, only the salty brine coming off the ocean on Omaha Beach hits the nostrils, the shrieks of seagulls pierce the ears and a sense of desolation hangs across the region's country roads. Fox News, 5 June 2020 Not quite in the same way as whisky fumes in the nostrils, though. The Economist, 23 May 2020 Draw deeply on the cigar, expand the nostrils to take in oxygen, reach slowly over the side of the tub to flick ash into the toilet. Katherine Dunn, The New Yorker, 4 May 2020 Those swabs, from all over Alaska, have been deep within the nostrils of people who might have the SARS-CoV-2 virus. Anchorage Daily News, 25 Apr. 2020 See More
Maggie O'neill, Health.com, 22 Sep. 2021 Manson allegedly returned a second time, covering one side of his nostril and blowing in Fountain’s direction. Michael Casey, USA TODAY, 18 Aug. 2021 The test -- the Pixel by Labcorp -- is designed for users taking a swab of their nostril and then sticking it into a solution. Matthew Vann, ABC News, 12 Apr. 2021 Failing and then flailing, a bored Reardon put a magnet in his nostril. Steve Mirsky, Scientific American, 26 May 2020 Heading into the D-Day remembrance weekend this year, only the salty brine coming off the ocean on Omaha Beach hits the nostrils, the shrieks of seagulls pierce the ears and a sense of desolation hangs across the region's country roads. Fox News, 5 June 2020 Not quite in the same way as whisky fumes in the nostrils, though. The Economist, 23 May 2020 Draw deeply on the cigar, expand the nostrils to take in oxygen, reach slowly over the side of the tub to flick ash into the toilet. Katherine Dunn, The New Yorker, 4 May 2020 Those swabs, from all over Alaska, have been deep within the nostrils of people who might have the SARS-CoV-2 virus. Anchorage Daily News, 25 Apr. 2020 See More Word History
Etymology
Middle English nosethirl, from Old English nosthyrl, from nosu nose + thyrel hole; akin to Old English thurh through
First Known Use
before the 12th century, in the meaning defined at sense 1
Kids Definition
nostril
noun
nos·tril ˈnä-strəl
: either of the outer openings of the nose through which people and many animals breathe
Medical Definition
nostril
noun
nos·tril ˈnäs-trəl
1
: either of the external nares
broadly : either of the nares with the adjoining passage on the same side of the nasal septum
2
: either fleshy lateral wall of the nose