Parallel

Parallel – two lines that run side by side and will never intersect

This definition is as I remember learning it as a child.

Parallel – extending in the same direction, everywhere equidistant, and not meeting http://www.merriam-webster.com/dictionary/parallel

http://library.thinkquest.org/20991/geo/parallel.html

Example:  http://math.about.com/od/geometry/ss/linessegments_6.htm