rarefy

• rarify

Borrowed from Old French rarefier (French raréfier), from Latin rarefacere (“make rare”). Surface etymology is rare +‎ -fy.

rarefy (third-person singular simple present rarefies, present participle rarefying, simple past and past participle rarefied)

1. To make rare, thin, porous, or less dense
2. To expand or enlarge without adding any new portion of matter to.

• stretch

• condense

• Frayer, Frayre, fayrer