Definition of "Pi" :

noun: an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs

noun: the 16th letter of the Greek alphabet

noun: the scientist in charge of an experiment or research project

noun: someone who can be employed as a detective to collect information

noun: the ratio of the circumference to the diameter of a circle; approximately equal to 3.14159265358979323846...