macronucleus

noun

mac·​ro·​nu·​cle·​us ˌma-krō-ˈnü-klē-əs How to pronounce macronucleus (audio)
-ˈnyü-
: a relatively large densely staining nucleus of most ciliate protozoans that is derived from micronuclei and controls various nonreproductive functions
macronuclear
ˌmak-rō-ˈnü-klē-ər How to pronounce macronucleus (audio)
-ˈnyü-
 nonstandard  -kyə-lər
adjective

Word History

Etymology

macro- + nucleus

First Known Use

1887, in the meaning defined above

Time Traveler
The first known use of macronucleus was in 1887

Rhymes for macronucleus

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Browse Nearby Words

macronucleate
macronucleus
macronutrient
See all Nearby Words

Cite this Entry

“Macronucleus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/macronucleus. Accessed 4 Nov. 2025.

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Medical Definition

macronucleus

noun
mac·​ro·​nu·​cle·​us ˌmak-rō-ˈn(y)ü-klē-əs How to pronounce macronucleus (audio)
plural macronuclei -ˌī How to pronounce macronucleus (audio) also macronucleuses
: a relatively large densely staining nucleus of most ciliate protozoans that is derived from micronuclei and controls various nonreproductive functions compare micronucleus
macronuclear
ˌmak-rō-ˈn(y)ü-klē-ər How to pronounce macronucleus (audio)
adjective

More from Merriam-Webster on macronucleus

Britannica.com: Encyclopedia article about macronucleus

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