pro

noun7

1. •
   A professional sportsman.
2. •
   (informal) Professional.

   • When it comes to DIY, he's a real pro.
3. •
   a good point about a plan or choice, thought about together with its bad points

   • What are the pros and cons of buying a car?
4. •
   (slang) A prostitute.

   • Millie was one of the dozen or so pros who had a house at the top of the street. — 1974
5. •
   A person who supports a concept or principle.
6. •
   (slang, historical) A chemical prophylaxis taken after sex to avoid contracting venereal disease.
7. •
   (slang, no longer used) A proproctor.

adjective1

1. •
   Professional.

   • He landed a pro mentorship gig.

preposition1

1. •
   In favor of.

   • He is pro exercise but against physical exertion, quite a conundrum.

noun2

1. •
   Initialism of patient-reported outcome.
2. •
   Initialism of pressure retarded osmosis.