What is the meaning of pi?

noun

• The ratio of the circumference to the diameter of a circle; approximately equal to 3. 14159265358979323846....
• Someone who can be employed as a detective to collect information.
  • synonyms: private detective, private eye, private investigator, operative, shamus, sherlock
• The scientist in charge of an experiment or research project.
  • synonyms: principal investigator
• The 16th letter of the Greek alphabet.
• An antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs.
  • synonyms: protease inhibitor