1. The art or science of determining position and course of a ship or aircraft by means of observations on board, whereby difficulties and dangers are avoided and a desired destination is reached as quickly and safely as possible.
2. The practice of passing on water of ships, whether inland or on the sea.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM