In aviation, an incident, often a crash, that is the result of a human decision or mistake instead of a solely mechanical failure. Although a mechanical problem or failure may be involved in the incident, it may be credited as pilot error if the cockpit crew or captain was aware of a problem and proceeded anyway.
An example of pilot error follows.
On January 13, 1977, a Japan Airlines DC-8-62 freighter, carrying live beef cattle to Japan, crashed shortly after takeoff from the Anchorage, Alaska International Airport. The plane was destroyed and the three crewmembers and two cargohandlers aboard were killed. The NTSB determined:
"...the probable cause of the accident was a stall that resulted from the pilot's control inputs aggravated by airframe icing while the pilot was under the influence of alcohol. Contributing to the cause of this accident was the failure of the other flightcrew members to prevent the captain from attempting the flight."
Source: http://www.airlinesafety.com/editorials/editorial3.htm