A significant alignment of sacred and secular sites across a landscape, generally inter-visible. The minimum number of aligned sites to qualify as a ley is five. The term was first used by Alfred Watkins in 1921. Watkins never used the term ‘ley line’.
There is no associated energy line indicated by the term ‘ley’ as Watkins described it, and therefore it is not to be confused with an Energy Ley.
(Source: British Dowsing, britishdowsing.net)