rarefy

/ˈrɛrəˌfaɪ/
verb
  1. To make something less dense, thinner, or more refined, especially air or a gas.
    • Heating the gas will rarefy it, causing it to expand.
    • Scientists rarefy the atmosphere in the lab to test how equipment works in space.
    • The machine rarefies the air inside the chamber to simulate high-altitude conditions.
  2. To make something more refined, subtle, or exclusive; to elevate or purify.
    • The strict admissions process rarefies the student body, allowing only the top applicants.
    • Years of study rarefied his taste in music, making him appreciate only the most complex compositions.
    • The poet's language rarefies everyday experiences into something beautiful.