rarefy

To make thin or less dense, as air.

To purify or refine.

To become thin or less dense.

To make rare, thin, porous, or less dense; expand or enlarge without adding any new matter; figuratively, to spread or stretch out; distend: opposed to condense.

To become rare; pass into a thinner or less dense condition.

To become less dense; to become thin and porous.

To make rare, thin, porous, or less dense; to expand or enlarge without adding any new portion of matter to; — opposed to condense.

To make rare, thin, porous, or less dense

To expand or enlarge without adding any new portion of matter to.

lessen the density or solidity of