v. (-ies, -ied)
1. tr. & intr. make or become less dense or solid (rarefied air).
2 tr. purify or refine (a person's nature etc.).
3 tr. make (an idea etc.) subtle.
Derivatives:
rarefaction n. rarefactive adj. rarefication n.
Etymology: ME f. OF rarefier or med.L rarificare f. L rarefacere f. rarus rare + facere make