1. Lessen the density or solidity of
   "The bones are rarefied" 
2. Make more subtle or refined
   - sublimate, subtilize, subtilise [Brit] 
3. Weaken the consistency of (a chemical substance)
   - attenuate

Derived forms: rarefying, rarefied, rarefies

See also: rarefaction

Type of: alter, change, modify, weaken

• proconsular
• proconsulate
• proconsulship
• proconvertin
• procrastinate
• procrastination
• procrastinator
• procreant
• procreate
• procreation
• procreative
• procreator
• Procrustean
• procrustean bed
• procrustean rule
• procrustean standard
• Procrustes
• proctalgia
• proctitis
• proctocele
• proctologist
• proctology
• proctoplasty
• proctor
• proctorial