rarefied (en)

(adjective) being less dense / (adjective) of, relating to, or interesting to a select group; esoteric / (adjective) very high / (verb) to make rare, thin, porous, or less dense; to expand without the addition of matter / (verb) to make more spiritual, refined, or abstruse / (verb) to become less dense

—p.66 My Stepdad's Huge Data Set (55) by Logic Magazine 7 years, 3 months ago