: a pouch within an animal or plant often containing a fluid
a synovial sac
Examples of sac in a Sentence
Recent Examples on the Web
This revealed that the creature had short arms, few arm suckers, and no ink sac, as well as having very smooth skin and a large rachidian tooth.
—
ArsTechnica, 1 June 2026
The shots induce the ovaries to ripen multiple follicles, the sacs that contain eggs, so that a surgeon can go in with a tiny needle, and drain the fluid in those follicles, which is then run into an adjacent embryology lab to search for the eggs.
—Lesley Stahl, CBS News, 31 May 2026
The proud parents decided to test the fluid around baby three’s sac to gain more information about the situation.
—Kayla Grant, PEOPLE, 29 May 2026
The sacs were eggs whose development had been arrested, as a result of the broader endocrine disruption.
—Veronique Greenwood, Time, 12 May 2026
See All Example Sentences for sac
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ArsTechnica, 1 June 2026
The shots induce the ovaries to ripen multiple follicles, the sacs that contain eggs, so that a surgeon can go in with a tiny needle, and drain the fluid in those follicles, which is then run into an adjacent embryology lab to search for the eggs.
—Lesley Stahl, CBS News, 31 May 2026
The proud parents decided to test the fluid around baby three’s sac to gain more information about the situation.
—Kayla Grant, PEOPLE, 29 May 2026
The sacs were eggs whose development had been arrested, as a result of the broader endocrine disruption.
—Veronique Greenwood, Time, 12 May 2026
See All Example Sentences for sac
Cite this Entry
“Sac.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sac. Accessed 9 Jun. 2026.
Copy CitationMedical Definition
sac
noun
: a soft-walled anatomical cavity usually having a narrow opening or none at all and often containing a special fluid
a synovial sac
see air sac, amniotic sac, dental sac, lacrimal sac
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