The pilot in command (PIC) of an aircraft is the person aboard the aircraft who is ultimately responsible for its operation and safety during flight. This would be the captain in a typical two- or three-pilot aircrew, or "pilot" if there is only one certificated and qualified pilot at the controls of an aircraft. The PIC must be legally certificated (or otherwise authorized) to operate the aircraft for the specific flight and flight conditions, but need not be actually manipulating the controls at any given moment. The PIC is the person legally in charge of the aircraft and its flight safety and operation, and would normally be the primary person liable for an infraction of any flight rule.
The strict legal definition of PIC may vary slightly from country to country. The International Civil Aviation Organization, a United Nations agency, definition is: "The pilot responsible for the operation and safety of the aircraft during flight time." Flight time for airplanes is defined by the U.S. FAA as "Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing." This would normally include taxiing, which involves the ground operation to and from the runway, as long as the taxiing is carried out with the intention of flying the aircraft.