as·​cus | \ ˈa-skəs How to pronounce ascus (audio) \
plural asci\ ˈa-​ˌskī How to pronounce asci (audio) , -​ˌskē How to pronounce asci (audio) , ˈa-​ˌsī \

Definition of ascus

: the membranous oval or tubular spore case of an ascomycete

First Known Use of ascus

1828, in the meaning defined above

History and Etymology for ascus

New Latin, from Greek askos wineskin, bladder

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The first known use of ascus was in 1828

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Cite this Entry

“Ascus.” Dictionary, Merriam-Webster, Accessed 24 Feb. 2020.

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More Definitions for ascus


as·​cus | \ ˈas-kəs How to pronounce ascus (audio) \
plural asci\ ˈas-​ˌ(k)ī How to pronounce asci (audio) , -​ˌkē How to pronounce asci (audio) \

Medical Definition of ascus

 (Entry 1 of 2)

: the membranous oval or tubular sporangium of an ascomycete
variants: also AS-CUS

Medical Definition of ASCUS (Entry 2 of 2)

atypical squamous cells of undetermined significance

Note: ASCUS is a diagnosis used in cytology to describe the presence of abnormal squamous cells in a Pap smear test. Upon staining, these cells exhibit an atypical appearance (as enlarged nuclei or irregular shape) that cannot definitively be classified as benign or precancerous.

Many physicians believe that combining the Pap test with direct virus testing may prove particularly useful when a pap test comes back with its most common indeterminate result, called ASCUS—atypical squamous cells of undetermined significance.— Jerome Groopman, The New Yorker, 13 Sept. 1999 Currently, there is no consensus on what to do with ASCUS patients, only 5% to 10% of whom actually have precancerous cells.— Rita Rubin, USA Today, 21 Feb. 2001

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