rarefy, v.
(ˈrɛərɪfaɪ, ˈrærɪfaɪ)
Also 5–6 rere-, 5–9 rari-, 7 reri-.
[a. F. raréfier (14th c., Oresme), or ad. L. rārēfacĕre (Lucretius), f. rār-us rare a.1 + facĕre to make; the form (for rārifacĕre) is perh. on analogy of ārefacĕre).
The pron. now usual in England has the vowel of rare adj.; the older usage, with the short vowel, is still favoured in America and Scotland (not dial.); cf. rarity.]
1. trans. To make rare or thin, esp. by expansion; to lessen the density or solidity of (a substance, now usually air or, in Path., bone).
| 1398 Trevisa Barth. De P.R. iii. xv. (Tollem. MS.), To hot sunne þat rarefieþ [1535 rerefieth] and openeþ þe pores ouer mesure. 1477 Norton Ord. Alch. v. in Ashm. Theat. Chem. Brit. (1652) 77 Water rarified becomes Ayre againe. 1523 Skelton Garl. Laurel 651 The clowdis gan to clere, the myst was rarifiid. 1659 W. Chamberlayne Pharonnida iii. iv. (1820) 67 Whilst choice music rarifies the air. 1677 W. Harris tr. Lemery's Course Chym. i. xiv. (1686) 347 A Coral rarefied and opened by the Spirit of Vinegar. 1756 C. Lucas Ess. Waters I. 44 Higher degrees of heat rarefy and expand water. 1871 Tyndall Fragm. Sci. (1879) I. v. 135 The hot wire rarefied the air in contact with it. 1897 Allbutt's Syst. Med. III. 149 The osseous structure..is absorbed, rarefied and softened. |
| absol. 1697 Dryden Virg. Georg. i. 566 As Rains condense, and Sunshine rarifies. |
2. fig. a. To make less gross or material, to refine, to purify.
| 1599 B. Jonson Ev. man out of Hum. ii. iii, You see..how their wits are refinde and rarefi'd! 1626 T. H. Caussin's Holy Crt. 24 Raryfying the most grosse thoughts, as the sun-beames doth the vapours of the earth. 1720 Welton Suffer. Son of God I. xi. 282 It is Prayer that..rarifies his Soul into an Essence of Divine Love. 1818 Hazlitt Char. Shaks. (1838) 142 Love is a gentle flame that rarefies and expands her whole being. |
b. To make (an idea) subtle.
| a 1699 Stillingfl. Serm. (R.), Plain truths lose much of their weight when they are rarify'd into subtilities. 1875 Jowett Plato (ed. 2) IV. 149 In some parts of the argument the abstraction is so rarefied as to become..fallacious. |
† c. To palliate, extenuate (a fault).
Obs.| 1622 H. Sydenham Serm. Sol. Occ. (1637) 222 There is something in this way, which may rarifie or extenuate an offence, nullify it cannot. |
d. intr. To discourse exaltedly.
nonce-use.
| 1928 Blunden Undertones of War iv. 44, I remember how Limbery-Buse and myself chirped and rarefied over some crayfish and a great cake. |
† 3. To reduce the number of (trees); to thin (a wood).
Obs. rare.
| 1650 Fuller Pisgah 411 Cedars were so rarified in Libanus, that modern travellers saw but four and twenty in their passage over this mountain. a 1661 ― Worthies (1840) III. 244 There needed no iron mills to rarify the woods of this county. |
4. intr. To become less dense; to be thinned.
rare.
| a 1658 Cleveland Committee 34 Bodies at the Resurrection are On Wing, just rarifying into Air. 1750 tr. Leonardus' Mirr. Stones 132 When it is kindled by fire, it rarifies, and is violently dilated. 1847 De Quincey Span. Mil. Nun Wks. 1862 III. 57 Like the mist sometimes rarefying into sunny gauze. |
Hence
ˈrarefying vbl. n. and ppl. a.| 1648 Hammond Serm. iii. Wks. 1683 IV. 487 This rarifying power of flames and judgments. a 1660 Ibid. xxiv. 641 This rarifying and purifying of the fancy. 1898 Allbutt's Syst. Med. V. 9 The common atrophic rarefying emphysema. |