plethysmograph

noun

ple·​thys·​mo·​graph ple-ˈthiz-mə-ˌgraf How to pronounce plethysmograph (audio)
plə-
: an instrument for determining and registering variations in the size of an organ, limb, or part resulting from changes in the amount of blood present or passing through it
plethysmographic
ple-ˌthiz-mə-ˈgra-fik How to pronounce plethysmograph (audio)
plə-
adjective
plethysmographically
ple-ˌthiz-mə-ˈgra-fi-k(ə-)lē How to pronounce plethysmograph (audio)
plə-
adverb
plethysmography
ˌple-thiz-ˈmä-grə-fē How to pronounce plethysmograph (audio)
plə-
noun

Examples of plethysmograph in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Offenders could be required to submit to plethysmograph testing, in which sensors are attached to their penis, in an effort to find out whether they were aroused by deviant imagery and sounds. —Christopher N. Osher, The Denver Post, 5 Mar. 2017

Word History

Etymology

borrowed from German Plethysmograph, from Late Greek plēthysmós "act of multiplying, pluralization" (from Greek plēthy-, variant stem of plēthȳ́nesthai "to increase in number" —derivative of plēthȳ́s "great number, multitude, crowd," derivative from the base of plḗthein "to be full"— + -smos, suffix of verbal action) + German -o- -o- + -graph -graph — more at plethora

Note: The term was apparently introduced by the inventor of a plethysmograph, the Italian physiologist Angelo Mosso (1846-1910), in "Von einigen neuen Eigenschaften der Gefässwand," Berichte über die Verhandlungen der Königlich Sächsischen Gesellschaft der Wissenschaften zu Leipzig, Mathematisch-Physische Classe, 62. Band (1874), "Sitzung am 19. December," p. 308. In a footnote the word is etymologized as "πληθυσμός abgeleitet von πληθύνω = füllen, vermehren" ("plēthysmós derived from plēthýnō = to fill, increase"). The word appears as pletismografo in an Italian version of this report: "Sopra alcune nuove proprietà delle pareti dei vasi sanguigni," "10 Settembre 1875," Giornale della R. Accademia di Medicina di Torino, serie 3, vol. 17, Anno 38 (1875), p. 215. English plethysmograph appears in reports of Mosso's presentations in Leipzig, as, for example, in the Philadelphia Medical Times, vol. 5, February 20, 1875, p. 330. The month and year of the first citation for plethysmograph in the Oxford English Dictionary, third edition, are both incorrect (an error carried over from the first edition). The passage in question was published in the June 24, 1876, issue of Scientific American (vol. 34, no. 26), p. 403, column 1.

First Known Use

1875, in the meaning defined above

Time Traveler
The first known use of plethysmograph was in 1875

Rhymes for plethysmograph

See All Rhymes for plethysmograph

Browse Nearby Words

plethysmogram
plethysmograph
plethysmothallus
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Cite this Entry

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

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Medical Definition

plethysmograph

noun
ple·​thys·​mo·​graph -ˌgraf How to pronounce plethysmograph (audio)
: an instrument for determining and registering variations in the size of an organ or limb resulting from changes in the amount of blood present or passing through it
plethysmographic
-ˌthiz-mə-ˈgraf-ik How to pronounce plethysmograph (audio)
adjective
plethysmographically
-i-k(ə-)lē How to pronounce plethysmograph (audio)
adverb
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