EVANESCE
evanesce, fade, blow over, pass off, fleet, pass
(verb) disappear gradually; “The pain eventually passed off”
Source: WordNet® 3.1
Etymology
Verb
evanesce (third-person singular simple present evanesces, present participle evanescing, simple past and past participle evanesced)
(intransitive) To disappear into a mist or dissipate in vapor
(intransitive, chemistry) To transition from the solid state to gaseous state without ever becoming a liquid
Source: Wiktionary
Ev`a*nesce", v. i. [imp. & p. p. Evanesced; p. pr. & vb. n.
Evanescing. (.] Etym: [L. evanescere; e out + vanescere to vanish,
fr. vanus empty, vain. See Vain, and cf. Evanish.]
Definition: To vanish away; to because dissipated and disappear, like
vapor.
I believe him to have evanesced or evaporated. De Quincey.
Source: Webster’s Unabridged Dictionary 1913 Edition