v. weaken the consistency; purify or refine; lessen the density
It becomes necessary to place the terminal in a bulb and rarefy the air in the same time.
Sentence in Classic:
The sun shone somewhat to the left and behind him and brightly lit up the enormous panorama which, rising like an amphitheater, extended before him in the clear rarefied atmosphere.
War and Peace(V4) By Leo Tolstoy Context
The sensation reminded me of my only experience of mountaineering, and from that I judged the air to be more rarefied than it is now.
The Time Machine By H. G. Wells Context