rarefaction
(rɛərɪ-, rærɪˈfækʃən)
Also 7–8 rari-.
[Noun of action f. L. rārēfacĕre: see rarefy v. Cf. F. raréfaction (14th c., Oresme).]
The action of rarefying, or process of being rarefied; diminution of density. (Now chiefly of the air or gases, or Path. of bones.)
| 1603 Holland Plutarch's Mor. 1318 To clense and purifie the aire by this rarefaction and subtilization. 1626 Bacon Sylva §30 In Gunpowder, the Force of it hath been ascribed to Rarefaction of the Earthy Substance into Flame. 1707 Floyer Physic. Pulse-Watch 69 In those Persons who have the best Tempers, the Blood and Spirits have a moderate Rarifaction. 1869 E. A. Parkes Pract. Hygiene (ed. 3) 466 In ascending mountains there is rarefaction, i.e. lessened pressure of air. 1898 Allbutt's Syst. Med. V. 605 In others there is..thickening or rarefaction of skull bones. |
| fig. 1672 Marvell Reh. Transp. (1675) II. 249 Lest they [laws]..lose in strength what they gain by extension and rarefaction. 1873 Symonds Grk. Poets vi. 171 Arriving at monotheism by a process of rarefaction and purification. |
b. With
a and
pl. An instance of this.
| 1834 M. Somerville Connex. Phys. Sc. xvi. (1849) 144 A regular series of condensations and rarefactions. 1873 W. Lees Acoustics i. i. 10 An undulation or wave..consists of two parts—a condensation and a rarefaction. |