: a median line
especially
: the median line or median plane of the body or some part of the body
Examples of midline in a Sentence
Recent Examples on the Web
The bands stopped precisely at the midline of her body, and the pigmentation of her right side was entirely normal.
—
Jerome Groopman, New Yorker, 6 Apr. 2026
All diffuse midline gliomas are categorized as Stage 4.
—Vanessa Etienne, PEOPLE, 31 Mar. 2026
The pectoralis major runs from the collarbone and breastbone to the upper arm and is responsible for bringing the arms forward, drawing them toward the body’s midline and rotating them inward.
—Daryl Austin, USA Today, 1 Feb. 2026
In a small clinical trial in New York, pediatric oncologists harnessed the technology to temporarily—but repeatedly—open the blood-brain barrier in three children with a rare type of brain cancer called diffuse midline glioma.
—IEEE Spectrum, 19 Nov. 2025
See All Example Sentences for midline
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Jerome Groopman, New Yorker, 6 Apr. 2026
All diffuse midline gliomas are categorized as Stage 4.
—Vanessa Etienne, PEOPLE, 31 Mar. 2026
The pectoralis major runs from the collarbone and breastbone to the upper arm and is responsible for bringing the arms forward, drawing them toward the body’s midline and rotating them inward.
—Daryl Austin, USA Today, 1 Feb. 2026
In a small clinical trial in New York, pediatric oncologists harnessed the technology to temporarily—but repeatedly—open the blood-brain barrier in three children with a rare type of brain cancer called diffuse midline glioma.
—IEEE Spectrum, 19 Nov. 2025
See All Example Sentences for midline
Cite this Entry
“Midline.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/midline. Accessed 10 Apr. 2026.
Copy CitationKids Definition
midline
noun
mid·line
ˈmid-ˌlīn 
: a line through the middle of something
especially
: a line through a body or one of its parts that lies in a plane dividing it into halves that are mirror images of each other
Medical Definition
midline
noun
mid·line
ˈmid-ˌlīn, ˌmid-ˈlīn
: a median line
especially
: the median line or median plane of the body or some part of the body
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